How about a Jr. dragster fuel cell? I'm using on that I mounted to a rear strut bar in the trunk. The one gallon Jr cell that I bought has 1 push vent on the top next to the filler cap and one barbed push in style fitting that includes a shut of valve. This IMO is perfect for water injection. The more common (not jr cell) 1 gallon fuel cell has too many fittings for water injection.
Use this and the Aquamist float sensor kit and the new bulk head adapter and your set to go.
Fuel cell (w/image):
http://store.summitracing.com/defaul...=egnsearch.asp
Bulk head fitting (w/image):
Waterinjection Forum Index ? ERL/Aquamist ? New tank adaptor (806-270) available now ....
Float sensor w/image):
Waterinjection Forum Index ? ERL/Aquamist ? Float level switch mounting question