Missing roundel

if one word would best fit as "rare" in signalling would be

flat roundels for back spectacles in purple or blue.

 

3 inches or 2 7/8 , have you seen one, let alone bought one.

I was thinking with some of my damaged purple lenses

i want to make a mold and cast my own glass with my

smelting oven i have ...

worth a shot as i could use a couple of roundels and for friends .

Done