We do have universal lids like the MaxxAir UniMaxx Universal Replacement Lid for RV and Trailer Roof Vent # MA00-335001 which would work fine for any roof vent on the market today so you could use that, or if you wanted a direct replacement lid we could do that as well. I would just need the make and model of your roof vent and I can see if we have it.
Also, for the membrane the closest I was able to get to what you're needing was the Alpha Systems Superflex TPO RV Roof Membrane # AL78CV... view full answer...