Well it COULD, but would cost you way more than just finding a buffered one. It will be difficult to find all of the parts, so some would have to be made. Unless you could do it yourself or find a friend that would do it for free, you should just buy one.
You sure the stock is non-buffered? I have seen others with IB date coded unbuffered A3 stocks, you're not the first.
Attached is the second A3 stock I bought from another member here back in late January/early February... And the rifle, I bought,used, from another member back in 2007 after returning from Iraq.
Is this HK93/33 A3 stock a buffered stock? Also, is there any value in a non buffered HK93/33 A3 stock?
The slim hand guard was from another HK Pro member too... I tend to buy everything HK here. Btw, I been a member since 2006 (AKA: Bergun), but I forgot my password AND the old email address I used to sign up with.