Yep, a DC PC cooling fan, like, a small hepa rated vacuum cleaner filter , a project box, the electronics to build a small dc regulator circuit, a sealed LA cell, probably 12v, and some wire etc. I would punch a hole in the back of the helmet, rig up the fan and the hepa system, and run a positive pressure system into the helmet. Keeps the head cool and provides virus free fresh air. You can get a full face PP filter setup, but who has a spare $500 sitting around? Mine cost me about $100. If the virus can't get in, then you don't get infected.

This would also help with hayfever (hint: original motivation for the application).

You have to get a fan that has enough cfm to overcome your respiratory volume, otherwise you will draw negative pressure on the inhale to hard and unfiltered air will come in the bottom of the helmet.

Or you could just wear a disposable particle mask and a set of goggles, but that doesn't look as cool.