Found them here:
For $1.88 each and reasonable shipping so I got some DICOR lap seal as well.
Thanks for all the clues. I'd still be looking for "LP compartment vents" which is what it does, but what it IS is a battery box vent.
BTW, the LP bottle compartment has virtually no floor, any leaked gas just falls out the bottom. This little vent just lets in some air to keep ventilation moving.