Where can I find an allergy/dust/antibacterial mask for kids?

[Allboxedin]

When I was in Asia everybody wore them when they were ill to stop germs and allergens ect.
Was just wondering what exactly they are called and where I can get one for a toddler.
My little one keeps having asthma attacks due to virus,winding up in hopsital so wondering if this could help?

They're an American company but will ship to the UK. Worth a try, I suppose.

Thanks oldlady, this has actually given me a little idea. I actually ordered a few from China!!