The scary fact is, if you get a bad localised reaction after being stung, if you get stung in the future it can then turn into anaphalactic shock. Doesn't happen with everyone, but can happen. I've only been stung once and that was when a wasp flew up the leg of my jeans and stung my calf. A week later it was still swollen, very itchy and painful.

Suggestion. Take your cycling helmet to your nearest motorbike shop and see if they could fit a motorbike helmet visor to it. I would think one for an open face crash helmet might do the trick. The only thing I can think of is fixing it to your cycling helmet could possibly weaken it.