Those fans are Conframo fans. You can get them in white or black from Defender Industries (a huge mail order marine supplier in Waterford, CT whose prices are 30 % less than West Marine on virtually everything). I got them and they push a lot of air, reasonably quiet, very nice.
Yes the mushroom vent seal CLC used is the same as door seal, same stuff as they sell for kayak hatches. But . . . if you install your mushroom vents correctly with the baffle pointing down, I don’t think you will need the gasket. I am at odds with the manual on this but will know for sure, I guess the first time I drive 65mph in the rain. The manual says they left insect screens out – not so, they omitted the rain baffles. For sure the rear mushrooms shouldn’t leak with their baffles in.
I installed a Hella marine (from Defender) light 15″ from the stiffener on the underside of my hatch ( on a 1/2″ plywood base matching its profile glued to the hatch underside. I hid the wire in a wood conduit between light and stiffener. There at the stiffener there are spade connector wire terminals. The wire from the electrical panel comes along the underside of the rain gutter andngoes through a hole in the stiffener. When I finally figure out how to post pictures, I’ll post some.