Assuming the top of the mask has lots of little vent holes, paintball masks tend not to take specific GoPro mounts but use various "universal" mounts that take advantage of the holes to bolt on. HK makes a popular one:

https://www.amazon.com/HK-Army-Goggle-Camera-Mount/dp/B07K38F8NG?th=1

Personally I'm a bit of a cheapskate and use a couple of these with the bottom sanded down flat: https://www.ebay.com/itm/323110485322?hash=item4b3ae2bd4a:g:3wUAAOSws6ZaJ6Mx&amdata=enc%3AAQAIAAAA0Oc1gCNbJNSLNuYG%2BeV62nb%2BFPqtUydDyNtyvjnkmZyr2TbywmBSGKiiQ8M0n5%2BRHSkPcbZWyA8k9ledF95srXvxieLSHzEUrQQ%2Fo6ovCoZW%2BR1aKlrIcy1iWVskPeaM4uMn%2FN%2BGEeM1NNMFNdvjSXqPeRInhGUr2%2FXaRp4h2iT29%2FkezXneiEvxhfi9Oqfk2XFlFWT91xbQcWhKuo8uqIAYwiPGv%2FauzXvjOt9e00QrefeZAT1ufqc5f1iKfrj4kcnWz33nZq1JFQkonicPnW0%3D%7Ctkp%3ABk9SR8zytsT\_YQ