I weathersealed my EOS RP for $5. DIY/Cool add on.

[mangobutter]

Love my RP, it's solid, well balanced, quite high quality. But the battery door bugged me. It jiggles around when shut and has an obvious airgap around the perimeter. There is a zig zag fitment which should in theory resist water intrusion to some degree, but I decided to step it up with stuff laying around the house. $5 insulation foam tape from ebay for automotive use. There may be better materials but I've been using this stuff to seal my film camera doors. Works great. The door now closes tightly and feels really premium. No jiggles. And now has an extra barrier for water to get through should I accidentally spill a drink on a table or something.

 

[Mark3794]

Did the same because i was bored with an old 1200d. I later tested it by spilling some water over the battery door. The insulating foam was soaked in water but i think it's still better than nothing

 

[Jethro]

Anything providing a bit more security for the battery door has got to be a good thing!

 

[mangobutter]

Yeah. If anything, it stops the battery door from jiggling around which annoys me since the rest of the camera is so solid.

 

[BlueBomberTurbo]

Been thinking of doing the same for the add-on grip (non OEM) for the EOS R. The battery door gets transplanted to the bottom of the grip, breaking the overall seal. So I'll just add some foam around the opening on the body side of the grip, and below the battery door on the bottom of the grip, like what the OP did.

https://images-na.ssl-images-amazon.com/images/I/514qTq3TcPL._AC_SL1200_.jpg