I have a chinese underfolder that is missing a few small parts. Does anyone know if other country stuff fits these the same as chinese parts would?

If so, anyone know where to get replacement parts?

I need the spring, threaded stem with outer lock, and a push button. Oh, and a trunnion too.

trunnion you're probably never going to find, the small parts though can be had from www.fbmginc.com/index.htm.  just look in "Tactical gear" then "Weapon accessories."  they're used and the stocks aren't pretty but all the parts are there.

I wonder then if a polish or a romy trunnion could be made to work, or maybe buy a complete small parts set to use with the stock.

This listing on GunBroker has a real nice photo of all the parts that needed to make a chinese underfolder work.  http://www.gunbroker.com/Auction/ViewItem.asp?Item=41406314  [Cut and paste]  -=NOTE=-  The chinese did not use any sort of additional trunion, block or whatever.  The receiver itself was stamped and cut to allow for the underfolder.  There was a "plug" that installed in the rear with 2 long rivets that also held the recoil spring.