Prying Eyes

Paint ball guns are too big and noticeable. Anyone have any ideas on a high powered squirt gun in a small concealable package -- like maybe CO2 powered from the same little powerlets they use for paint ball, feeding a tank in a fanny pack, up a flex tube in your sleeve to a nozzle in your hand. Shooting a fine stream allows easy aim correction, and you could even use the thing inside buildings more easily. Make it all plastic if possible, so to evade metal dectors. Could also fill tank with DMSO and nicotene and have a deadly weapon. Or just a knockout weapon.