First off I responded to this already. The people who I knew selling them are not at the moment. Why a mold would have to be made is just crazy. Any good 3D printer would do the same thing. There was 3 people 3D printing them and selling on EBay. I asked one if he could make a few and he told me when he gets a chance as 3D printing for him is his business. When I get done with my project I will also make a few either in a printer (synthetic) or on my CNC machine out of aluminum.
This is not Apollo we are not building the lunar lem. Simple is always better.
There is a ready market, and this was pretty extensively discussed here a while back. Nobody came forward with either a source or even a hint of anyone producing them. The situation hasn't changed as near as I can tell, I still don't know of anyone besides Henning's that is now producing them, or even planning on it.
If someone is now, or has in the past, produced a replacement sideframe for the Lionel scale JLC GG1, please point it out to me.