That all depends on what you want to do with it and how much you're willing to spend.
For a normal rifle scope, you could get a Belarus BP-01 and still use you iron sights:
BP-01Or you could spend a lot more and get a KVAR mount:
KVAR's mountsIf you're mounting a red-dot or you want a low mount, you could get a BP-02:
BP-02or if you're not afraid to do a little work , you could get an Ultimak:
Ultimak,
As for places to order, I've personally ordered from
Freedom Optics and
Ultimak.
But finally, don't forget to check the
EE under Optics & Sight Equipment and AK Mags, Parts & Accessories.