You can probably buy some copper wire and try making your own!
A while ago I found this tutorial on wire wrapping which is really useful
For supplies you could try Beadaholique.com It is pretty good for general beading and crafting supplies. They also have a Youtube channel with lots of crafting tutorials.
Riogrande.com is also a really great resource for wire and tools.
If you were looking for ready-made holders, I found these bead cages on Amazon (silver colored) and (golden colored) but I’m afraid that’s what you were trying earlier.
I would suggest to look at the dimensions so that it can fit your crystal exactly. Let me know if that helps!