If anyone has some leftovers they could post to Hungary, I would be very happy to buy them. Thank you.

Sorry, I don't have any. But by my math that works out to about 2.25 mm in diameter. Could you make them out of solder and then flatten them a bit?

I've seen the PE ones in some of the Trumpeter kits and they just look too two dimensional to me.

Shapeways does them as well if you can get by with only one kidney.

You might also try a hole punch on some sheet plastic and then drilling out the center hole. I've purchased several punches with different diameter sizes from sewing and craft stores. I've used some 3mm disks to make shields for some 10mm ancient figures. the tricky part is not feed them to the carpet monster when painting.
John

Thank you for the suggestions. I may try the soldering wire solution (although right now I feel like I really just want to finish the build, and slapping on some pre-painted PE looks mighty attractive )