I have some experience creating parts in FreeCAD for 3D printers, and have also struggled to find replacement parts, so have vaguely thought about modeling up some sort of printable replacement headshell/tonearm socket for the Elac Miracord 50H.
At first I thought about this from the angle of replicating the existing headshell and connector for backwards compatibility with existing parts. It seems doable, but you'd need to incorporate part of a standard off the shelf pin header into the design somehow, as well as the grounding plane, and I have no idea how to do that in a way that will always work. It would also have to be a simplified design; I'm not an engineer, so there's no way I'd be able to replicate the lead screw adjustment sled assembly (though arguably if one could just print a new head for every cartridge they own, the inconvenience of mounting them just once isn't that bad.)
The other angle I thought about was if it would be possible to design something that replaces the existing connector with one that makes standard Technics headshells fit instead. Basically just a housing for a run-of-the-mill socket connector you can source on ebay, and then you're just out of the proprietary Elac ecosystem entirely. The problem is that the Technics style headshells are quite a bit longer than the Miracord headshells, so it wouldn't actually be that easy to design while keeping the original tonearm length intact, unless somebody makes Technics headshells which are much shorter than standard.