Anyway I've got some cool ideas. So what about instead of CO2, we use a small water pump. you can get one at most walmarts for like 15-20 bucks. each are smaller that the average CO2 cartridge. Now, it would need a 9 volt battery, and the web fluid would need to have the viscosity of water.
Also, what about, and this is only if your not using a cartridge, instead of using a tank, you could use a water bladder. They're cheep, strong, flexible, easy too remove and clean, and if you were to strap it to your back, no one would notice. If you want to use a big one, put it in a back pack, and then you could also fill it with other stuff.
I also have another idea for web fluid expulsion, but I'm saving that little tidbit for later.