So you can install formic pro and other formic acid products without an actual mask if you are using it outdoors. You can certainly get a good whiff of it, but as long as you don't bury your face in the stuff its fine. You ABSOLUTELY need to wear chemical resistant gloves though. Safety glasses are good to if you are treating a lot of hives that day.
As far as masks, you may be confusing this with oxalic acid sublimation, in which you absolutely must wear a mask when applying since the sublimated chemical will redissolve in your lungs if you breathe it in. Formic strips are slow release and will not put that much into the air.
But if you want to wear one, all you need is something like a 3M respirator with filters that are rated for Organic Vapor/Acid Gas. They make loads of different cartridges. The ones I use are from 3M and have these big pink and yellow filters on them.