Where can I get 16mm and 20mm insulator gaskets like this or similar?
Intl-Outdoor have some:
http://intl-outdoor.com/components-gears-c-57_106.html?page=2&sort=20a
Cant tell if there flat or have a bit of a step in them. Got a bit thicker gauge wire to clear.
RMM has a few kinds, very thin adhesive rounds and the butterfly style with the centering ring.
I don't know if I've ever seen a spacer like for sale anywhere. If you've got thicker wire to clear, it would make sense to use a thinner gasket though if you want the space between the MCPCB and reflector to be the same.