something that could plug into the vent that I could lay outside the cover.

With the cover off, the Nicro vent works very well. One small vent is enough to keep the boat fresh.

But I want to put on a loose full boat cover (not shrink wrap) to protect the deck and brightwork. I also obviously want to keep the vent working.

I looked at their web site and didn't see any solution to this... so I suspect I will have to just work something out. Maybe I can take the solar panel off the old one and wire it to a connector and find a way to add a connector to a new one to make this work.

I was simply wondering if anyone else had come up with an elegant solution.

Always nice to toss ideas around here.

Yeah, I've seen those heater things.