I actually found it on Amazon here

depends what style you want to go for it. looking for it myself, i cant actually seem to find that specific mask used in the picture. what i recommend instead of that is the Payday 2 version of the Richard Mask. I wore it for halloween and imo it works so much better. It still keeps the point that you're cosplaying as a mass killer for fun, without it being too creepy that people who dont know the game will be freaked out by you.

If you feel the payday 2 version is too cartoon-y or something, search this on amazon instead.

If you want my very specific recommendation, I got this mask, but it does appear to be out of stock right now. the other versions are about as good anyway though.

https://www.amazon.com/dp/B06XX92JLD/ref=cm_sw_r_cp_apa_i_dYY.FbXFWTZGG?_encoding=UTF8&psc=1

might want to look around on Amazon for a cheaper one though

there's multiple on Amazon, i know at least three. here's the one i bought, though

https://www.amazon.com/dp/B06XX92JLD/ref=cm_sw_r_cp_apa_i_dYY.FbXFWTZGG?_encoding=UTF8&psc=1