If someone else casts collaborative thaumaturgy as you cast a spell that'd do it. This is obviously a difficult thing to arrange on a regular basis unless you take the leadership feat, and you say you can't spare any feats.
It works with Familiar spell (not available until mid-level, but it's ok). I have to think about it (the cost is heavy, but i think there's something to do with this). x)
Note: i *could* spare a feat on leadership since it's the best feat in the game(ie, it's a better feat than any of the feat I'll ever take), but I *won't* do it because it's too cheesy. I have no problem with Improved familiar + Familiar spell: my "cheese limit" is at improved familiar with UMD cheese (I don't know if it's inside or outside my limit; Familiar spell has a real cost, so it's inside the limit). Leadership is far outside this limit.
Edit: I suppose if you dump your mouthful as a move action that works without taking your swift or standard actions. Maybe your familiar can grab the dumped item and run.
That, or an Unseen servant...
I already though about the Unseen servant, but in the end it's the same as having the unseen servant holding some stuff and no cheek pouch...
Note: I have still one Trait to choose, and i'm considering Accelerated Drinker. The combo with cheek pouches is obvious... If i can actually use my cheek pouches x) . Or maybe I shouldn't take this trait at character creation (and take Magical lineage + Accelerated drinker at level 15+... i guess it's worth a feat, since magical lineage is worth a feat all by itself x) ...)
The other trait I'm considering is Sleight of hand as a class skill. Not very useful, but the idea of stealing something and hiding it in my mouth is a lot of fun at least. x)