I bought my Airforce Sistema at a gun show. It was a little rough with a shot out barrel. Another vendor had new GI barrels for $40 and I bought one and took it and the gun to a third vendor who took the link and pin from the old barrel and installed them on the new one for $2. Works fine.
The mag that came with the gun also was bad, so I bought some surplus mags and they work great.
AFAIK, any part that works on the original Colt will work on the Sistema.