I looked back at your original thread to remind myself what we are talking about. You specifically want a sideplate and retainer nut for a .38 Double Action, Second Model. These top-breaks came in different sizes and the sideplates are not all the same (though I think the second and subsequent models of the .38 DA were dimensioned and shaped the same).
You might query Dave Chicoine at
oldwestgunsmith.com or the folks at Jack First (
Jack First Gunshop).
Your gun is nickel, right? In the best of all possible worlds you would want nickel replacement parts, but you should take what you can get. Your first goal is to restore this gun to operating order. You can make it look pretty -- or at least prettier -- later on if you are so inclined.
Once again, I want to warn you about throwing too much money into improving an old-timer. I'm not sure that one is worth restoring or refinishing, but if I had it I would definitely try to find the missing parts just to restore its functionality. But I doubt I could justify paying somebody else to work their magic on it.
AFTERTHOUGHT: In another post I said you might need a gunsmith to fit a non-original side plate. That's not necessarily true. If you have patience and good eyes, you can do it yourself. Just remember that you can always take more off, but you can never put any back. So realize you are working in thousandths of an inch, work only on the high contact points, and you should be OK. If you get a replacement sideplate that is just a little loose (but not gappy) and drops right in, I'd consider that OK.
