I got a Bell Metropolis that came with a snap-on rain cover. Hi-vis would be nice, but this one fits so snugly that I'll forgive its low-vis black n' gray color.
Any rain cover you get will certainly make rain riding much nicer. I got caught in a downpour with a regular helmet and could hardly see from all the water rinsing sweat into my eyes and covering my glasses. With my Metro, it's not a problem at all.