Vent Cap Ideas Needed for Airhead

[Ramble]

Rather than replace all the old plumbing in my new to me Niagara 31, I went with an Airhead. I'd like to vent it out the side of the cabin house to keep the space around the mast partner clear of obstructions. Some of the vents I've seen like the flying saucers are too large, others like the Vetus mushroom caps don't look like they would keep much water out when used on a vertical surface.

Anyone have any suggestions on a: 1) small, 2) effective vent cap for a 2" air exhaust hose that could be used on the vertical side of a cabin house?