Actually, I used a PVC container strapped to my back for the fuel. It just had a metallic shower cord strung up through the thing to prevent the super soaker from melting before it could make a decent shot. As for the flame element, one of those lighters that isn't easily extinguishable by wind.
Also, there are several videos of people doing this all over Youtube. So you can watch and enjoy them playing with them. Note the lack of consideration for said fuel air ratio in most of these videos. It either isn't that important or a 13 year old knows a lot more than we previously imagined. I'd think the first one. I had access to racing fuel.