I discovered this on guns.ru forums.
This guy Dmitry in Novosibirsk, who has been doing this for a while and is reputable, makes custom polymer stocks for all kinds of guns, including the Vepr Super.
Here's his basic one:
Here's his adjustable one, which is bout 2x the price:
Here's a prototype that he's working on right now:
Just thought I'd share. I'd love to have that adjustable stock.
Edit: Fixed the images, by attaching them here, instead of linking to guns.ru