I spoke to a gunsmith about some kind of plastic inserts that you could use, he said he didn`t know of anything on the market that would fill the bill, what he suggested was to cover the frame with tape so if and when you sand,file,use dremel etc. you won`t mar the surface unless you stay too long maybe a couple layers won`t hurt until you get real close to matching pieces together, go slow and carefully remember what the old stock maker said "you can take it off easily putting it back is a little harder" Good Luck.