Ok, so from what I understand, duckbill mags are hit or miss(usually miss), Hitech mags are not a sure thing either and AK 47 magazine conversions are difficult, complex and largely impractical.

I know there are Chinese SKS-Ds and SKS-Ms that take AK mags as standard--are there any  models of these that included a folding bayonet? If not, would it be theoretically possible to remove the SKS-D/M barrel, remove a military SKS barrel from another rifle and install it to the SKS-D/M reciever so that you'd have an SKS that takes AK mags but still has the folding bayonet?

im not completely sure on this but i think that would violate 922r

There were models that had the bayonet.  I had one and sold it in 96, I've been kicking myself ever since