I actually had to do this the other day, if you mean the lens holding gasket. I cut some walleva juliet armsocks I had on both sides to be thick enough to sit in the frame. Holds the lenses in place well enough, but still a little wiggle room. Eh, it works I suppose.
I ordered a 419 piece O Ring set hoping to find a suitable size O-ring or something.. guess what, I still have 419 O rings that are unuseable in the Romeo 2.