For the UK/EU types, GVS make a good half resporator mask:

https://www.gvs.com/en/catalog/elipse-p3-respirator

This one is good for standard DIY duties that do not involve chemicals (ie cutting, grinding, sanding)

there is a quite readable guide you can get here: https://www.hse.gov.uk/pubns/priced/hsg53.pdf

For chemical resistance: https://www.gvs.com/en/catalog/elipse-a1p3-respirator

BUT you need to worry about mucus membranes (ie eyeballs can absorb some chemical). The A1 bit means that it'll protect against PPM that are less than 1000, (No I don't know what the PPM of teargas is.)

I guess but cannot assert that decent hardened safety goggles will help against gas in the eyes, but again you'll need to look at the standards for that. the all in one mask/face shields are a better bet.

Your local hardware store should carry this kind of stuff, especially if they do any kind of plastic solvent or fibreglass/epoxy stuff.