My Saiga has a number of the features you mention straight out of the box.
Picatinny rail, magwell, uses associated mags which just slot in straight and drop out when mag release is used, manual bolt hold open, flash suppressor, AK foresight sight, IZMASH pistol grip
I got it from Oleg at www.rusmilitary.com but they are 24" barrels to comply with UK law. They are made by Legion which is some kind of associate company or otherwise of IZMASH
Here is a pic