This is an interesting thread for me, and it would be great if someone did find a mouth mask that didn't make you look like a relative of Darth Vader.
Almost all of my cycling is along quiet country lanes and tracks, so the bug population at certain times of the year is a steady facial bombardment.
I always wear glasses now, and I have a couple of wraparound pairs that work well and don't make me look like I should be wearing Lycra, so that's solved the eyeballs problem.
I try to keep my gob shut, but I've had a few close calls with bumble bees crashing off my cheeks while my mouth was slightly open, so the possibility is quite worrying.
What we need is a simple flesh coloured triangle of plastic with a fine mesh. Surely it exists somewhere on this planet ?