Spells

A fair number of spells prevent teleportation; a wizard will struggle to gain access to some of them, but the skill Use Magic Device and a wand or staff will solve that.

• The 4th-level Sor/Wiz spell dimensional anchor [abjur] (Player's Handbook 221) for 1 min./level prevents 1 creature from using any extradimensional movement if a ranged touch attack succeeds versus the target.
• the 4th-level Sor/Wiz spell Otiluke's suppressing field [abjur] (Complete Mage 112) for 10 min./level in a 20 ft. emanation stops all spells from a particular school; conjuration is the obvious choice.
• The 5th-level Sor/Wiz spell investiture of the orthon [trans] (Fiendish Codex II 104-5) for 1 min./level grants the caster a 20 ft. radius aura that prevents of extradimensional movement like the spell dimensional lock.
• The 5th-level Clr spells hallow [evoc] (PH 238) and unhallow [evoc] (PH 297) for 1 year when the spell dimensional anchor is tied to the hallow or unhallow spell prevents extradimensional movement out of an area. This is the house rule I use as there are no guidelines that describe what tying the dimensional anchor to the hallow and unhallow actually does.
• The 5th-level Sor/Wiz spell zone of respite [abjur] (Spell Compendium 244) for 1 min./level in a 20 ft. radius emanation prevents extradimensional movement and summoning into the area.
• The 6th-level Clr spell forbiddance [abjur] (PH 232) permanently prevents extradimensional movement into or out of an area.
• The 8th-level Sor/Wiz spell dimensional lock [abjur] (PH 221) for days prevents extradimensional movement into or out of an area.
• The 9th-level Sor/Wiz spell Halaster's teleport cage [abjur] (City of Splendors: Waterdeep 155) permanently prevents teleportation into an area and sends the would-be teleporter somewhere random on the plane, while allowing teleportation within the area but sending the would-be teleporter somewhere random within the spell's area.

If the wizard doesn't have to use teleportation effects himself to escape he should probably employ the spell dimensional lock. If he does have to use teleportation effects himself, he can use the feat Chain Spell (CAr 76) to modify the spell dimensional anchor.

Magic Items

The best magic items are scrolls, staffs, and wands of the above spells, but specific magic items are also useful.

• The weapon special ability binding (Magic Item Compendium 29) (+1 bonus) makes a stabbed victim unable to teleport.
• The rod soul anchor (MIC 185-6) (10,000 gp; 3 lbs.) prevents adjacent creatures from moving from their squares. It's difficult to use because of the positioning required and allows a saving throw.
• The slotless item dimensional shackles (Dungeon Master's Guide 255) (28,000 gp; 5 lbs.) prevents teleportation, but getting them on the guy who's doing the teleporting while he's conscious might be a challenge.
• The slotless item weirdstone (Player's Guide to Faerûn 124-5) (250,000 gp; 0 lbs.) is the ultimate method, preventing teleportation into a city-sized area, but not stopping teleporation from inside the area to outside the area. In this situation, it's both ineffective and overkill.

A Few Notes about Teleportation
The presence of teleportation magic changes many of the core concepts of pre-teleportation adventuring. Certainly mere travel time is shortened, but if teleportation is at all a consideration in the campaign world, smart rulers will liberally ward many structures with hallow or unhallow (if only so the teleport invaders must exit the structure to teleport again if using the house rules above). The cave in your question is the kind of place that wouldn't be already so warded, but it's nonetheless something to keep in mind for your campaign.

Also, the spell teleport [conj] (PH 293) explicitly says, "Areas of strong physical or magical energy may make teleportation more hazardous or even impossible." In that quotation the word teleportation is not italicized--that's teleportation in general. The DM can just say No to teleportation effects in any area and claim, "It's strong magical energy prevents teleportation." The wizard might've chosen the cave in the question for precisely that reason, although that may seem contrived to the players.

Players who go Dumpster-diving for travel solutions will eventually find the 7th-level Drd spell master earth [trans] (SpC 139), a transmutation spell that sends the caster anywhere on planet by shoving him (harmlessly, obviously) through the planet. I've house ruled this spell so that it cannot penetrate creature-built structures and instead moves the caster to their most common entrances. (The spell itself says, "Underground, creature-built structures don't hinder [the caster] as long as [the caster] can move around them," and I've expanded that to mean the caster can't enter any creature-built structure using the spell master earth.) Further, they might even find the never-errata-ed and never reprinted 9th-level Drd spell lookingglass [trans] (Masters of the Wild 90), whose effects I urge house ruling to actual clairvoyance and to actual teleport without error (i.e. greater teleport) instead of as if those spells. With the existence of these spells in the campaign and without house rules, high-level druids are the ultimate assassins.

Finally, a spell clock (Clockwork Wonders column "The Spell Clock") (130,000 gp; 0 lbs.) that's crafted at a high level by some ancient epic precursor and that was toted around the campaign setting could create a worldwide forbiddance effect—useful if the DM doesn't want to deal with teleportation effects at all ever.