Good question! And one every GM has to deal with from time to time I would think. I'd probably pick one or two of these:
Keep the pace. Part of your story revolves around urgency. Let them feel stressed out, make your encounters heave for breath, more so the closer the party gets to the final boss fight. Try to make them feel guilty for even the slightest pause, thorough searching etc.
Help them recover. Let the PCs discover an old and forgotten crate with a nearly empty healing wand, some crumbling restoration scrolls and a six-pack of useful potions with faded labels.
Surprise the badguys. Villains also need to deal with changing schedules.
- An important ritual component is lost or spilled on the floor during preparation and a minion is dispatched to the nearest town to procure more.
- A pair of blundering ogres accidentally discover the villains hideout and must be dealt with, depleting resources.
- A cloudy night sky diminishes moon power, so the ritual is postponed for a day or two until weather clears up.
- The players can mess up the villains schedule. Give them a chance to funnel a swarm of dire bats into the villains part of the dungeon, thus creating havoc and buying time.
None of the 3.5 classes or feats that were released in "splatbooks" (books besides the core three) are likely to ever appear in Pathfinder, owing to legal issues. Basically, they're considered Wizards' Product Identity, not Open Game Content, and can't be copied by Paizo, the makers of Pathfinder.
However, Pathfinder is fully 3.5 compatible. You can play the Warlock as written or modify it to be more like the updated Pathfinder classes and it should work, rules-wise. You might have some occasional issues that require some GM adjudication, but for the most part the class should work just fine. This is true for virtually every splat-class in 3.5.
As far as official Pathfinder suggestions go...
Thematically (fluff-wise), the Witch is pretty near a Warlock. Power from a (usually dark) otherworldly Patron, certain special abilities that aren't limited in uses per day, lots of manipulation and control abilities. But I don't think that's what you're going for.
Mechanically, the Kinecticist is nearly a Warlock. Most of his abilities are unlimited use, he has a thematic and modifiable blast power as one of the cornerstones of his class, his utility powers will vastly differentiate one from another. You might want to consider it.
Best Answer
There is no direct analogue. The closest might be the Nagaji from the Advanced Race Guide - but you can browse all the official races on the SRD and see what might capture dragonborn-age the most to you.