Drink half a pint of milk before a large session and again after if you can stomach it, milk helps get rid of the zinc outa your system.
No point buying online, too expensive. Find a local steel merchant/fabricator.
If you go to a welding/engineering shop you will normally find the lads in there know where the fabricators are because they sell consumables to them, you can also ask them about zinc poisoning and if a mask is available.
I know the lads (and the gaffer) at our local sheet metal fabricators and he advised milk but mainly ventilation! Nobody there wears any kind of respiratory device so I guess there is nothing available.