[Spktyr]

Colt used to make them. Olympic Arms and DPMS still make them.
Bushmaster made some for a while, dunno if they still make them. They're growing in popularity again.

That said, *my* AK fires 12ga slugs (or shot).

[kerryusama04]

I use a mossberg for the 12 gauge.

This is what a yahoo search turned up. The two manufaturers do not list 7.62X39 rifles on their sites. It seems to be an aftermarket/kit thing.