The barkbuster type with the aluminium bar are probably the only thing that will help with that. The Suzuki plastic ones do give better weather protection, but they do flex easily enough to ruin levers, and then pop back into place as if nothing has happened...
The other alternative is folding levers? Plenty on that well known auction site for cheap from Hong Kong. Not fool proof, but they'll usually fold themselves out of the way instead of breaking.