Reddit mentions of WoodyKnows GP Nasal Mask

I don't know if this would work for you but (I kept hallucinating from the formaldehyde and this cut the odor and effect for me tremendously, along with the odor from the cadaver) I bought a few gas and pollution reducing nasal filters like this one. They're fairly discreet and slip into your nostrils and are connected by a thin band to fit. It can be cleaned with alcohol and isn't as bulky as a more efficient full-on chemical safety mask but not as inexpensive as a camphorated unguent like Vicks, either.