“I have often thought of building a buttstock for a break action single shot that has a built in “pez dispenser” like shell dispenser”
I think Rossi makes a gun like that. Simple single shot, polymer stock, with shell storage.
At least I think it was Rossi.
The reason I used a velcro attaching system for a stgrip of shells is that the ammo and gun can be stored separately from curious little hands. The Rossi shotguns are very good quality, BTW. That;s what I used for my systems, too.
Sounds like the poster would like a Saiga. And yes, Rossi makes a shorty with thumb-hole and four shell slots in the stock.