Neoprene face mask, but you'll sweat alot.
I DIY mine from a Sensei lower face mask coupled with a Bolle goggles. I follow the instructions from here:
DIY Sensei X800 Goggles - Filipino Airsoft (FAS)
It's written in Tagalog (Philippine's language), and since I don't speak Tagalog as well, I believe the picture is self explanatory...