Could they be
3d printed? Pictures might help... 
 There are actually two varieties. The plastic ones probably could, but actually I was
  talking about the steel ones which probably can't. I have put it all away again for
 now so I can't get any pictures right now. I'll get it out again later, if I can,
and post
 some pics. 
 
Could you turn them on a lathe. I assume they're quite small.
-tony