While I applaud the wizard's chutzpah...

The Accidental Activation Rule Is Terrible

I fully agree with KRyan and Ernir that ignoring the accidental activation text is the best way to go. It causes more problems than it solves. I'm of the opinion that it's included only so the DM can have hilarious situations occur at the tavern because the wizard forgot the command word for his wand of fireballs was hubba hubba.

But If You Must Use It...

If you're dead-set against totally house-ruling it away, here's one way to run it.

The command word text reads, in part,

A command word can be a real word, but when this is the case, the holder of the item runs the risk of activating the item accidentally by speaking the word in normal conversation. More often, the command word is some nonsensical word, or a word or phrase from an ancient language. Activating a command word magic item is a standard action and does not provoke attacks of opportunity.

Emphasis mine. Not possessor, by the way. The holder specifically--as in what one does with a hand.

The description of the pearl of power reads, in part,

This seemingly normal pearl of average size and luster is a potent aid to all spellcasters who prepare spells (clerics, druids, rangers, paladins, and wizards). Once per day on command, a pearl of power enables the possessor to recall any one spell that she had prepared and then cast that day. The spell is then prepared again, just as if it had not been cast. The spell must be of a particular level, depending on the pearl. Different pearls exist for recalling one spell per day of each level from 1st through 9th and for the recall of two spells per day (each of a different level, 6th or lower).

The wizard can create multiple pearls of power all with the same command word. The wizard can activate one pearl of power in the wizard's possession as a standard action using that command word. If the wizard holds in her hands two or more pearls of power when the command word is spoken as a standard action to activate a magic item, one of the pearls of power in wizard's hands activates, determined at random.

(This assumes that the DM determines that a held magic item takes precedence over a merely possessed one with the same command word and that the DM wants to stick to the (actually far more important) rule that activating a command word magic item takes a standard action, and therefore simultaneous magic item activation can't happen accidentally, much less, like here, as some kind of faux accident. I went with random determination as that makes sense if multiple pearls with the same command word are deliberately held and the holder fails to specify which one to activate when the command word is spoken.)

You don't need to use only the standard magic itens.

Magic itens, as all rules on Pathfinder, are guidelines, not something written on stone. You can always create your own magic itens, according to your needs. If you want to go that way, just check a similar item that does what you want (Let's imagine a Gloves of Giant Might, +4 STR) and change the bonuses to something else.

That's said:

This page contains a bunch of core pathfinder magic itens. While it is not on a CSV or database format, you can simply use Ctrl+F and search for Constitution (or any other score) to find what you are looking for.

My suggestion, however, is using a bit of GM Trickery to solve this issue. If you want to raise the Con value of a single character:

• Organize an encounter where the players find a helpful druid, wich uses some "experimental magic". Show them some random magic spells, completly different from anything they know - things like Explosive Butterflies of Doom or Homing Hummingbird (Like a Magic Missile, but with force-birds).
• Keep the druid around and give the players a small quest, to help him do some stuff. Make the druid promise some nice, but exclusive, consumables, like "Potion: Mass Cure Moderate Wounds" - you drink, all the party gets healed.
• When the players are almost going away, after saying goodbye to this crazy druid, make something appear from nowhere, like a huge ogre. This ogre hit the Druid with his club, making him fly away inconcious, leaving the party to face it alone.
• Kill the Low-Con character. Use hidden combatants if needed - a Wizard using Save-Or-Die, con-based spells would be nice.
• When the party kills the Ogre, the Wizard runs away.
• The druid wakes up, and Reincarnate the fallen combatants. This reincarnation, however, as his other spells, is experimental and thus could have "unexpected effects". Use this to change his values around and raise his Con, while keeping his appearence.

It will depends on your party, but it could solve your issue. I used something similar trying to solve a Low-Int issue, where the druid, after the reincarnation, said that the "low-int" was because of a crayon stuck on the brain of the character, but the reincarnation gave him a Crayon-less skull.

We got a bunch of laughs, the players got really happy, and everything went fine!