Flurosilicone O ring help.

Hello I am after a few FLUROSILICONE O rings for a solarforce L2D build.
the AR lens is 28mm if that helps.

any idea of the size(s) I would need and where to get from ?.
I have emailed sinner too.
Anyone else?.

thanks.

Not sure about the L2D but Sulman uses #18 orings I believe