A "camelbak" is a water hydration system. A lot of hikers, runners, bikers, etc. will use them.
There are also "military" ones that have Molle systems to attach pouches and stuff to it and have camo patterns on them.
Camelbak is a brand but "Hydration System" is the name for it (kind of like "Frisbee" and "Ultimate disc").
I really have no clue whether or not a neoprene mask is enough. It should reduce the energy enough that it will probably hurt but won't chip your teeth. As for bandanna I don't think it will reduce the energy enough (or at all) but it does look badass. I know however that some people use a shemagh and tie it around their head, and because it's "layered" and "loose" it absorbs a lot more energy (like a cushion or crumple zone) when the BB is going for your face.
Please note however your mileage may vary. This is from my experience and what I know (Actively playing airsoft for 2 years and "chairsofting" for 6).
PS: If you're in Toronto, Army Issue Surplus in Port Credit (1 Stavebank Rd North Mississauga ON) will get you verified AND sell you gear too. Another place is "Huangs Outdoors Shop" (Unit 393, 4438 Sheppard Ave Third floor in the Oriental Center at Sheppard and Brimley, Toronto).