Sounds to me like the Spring-Airs may be your best bet. Their website is http://www.retracts.com/index.html and that has a phone number. Give them a call and talk to Bill Watten, who runs the place. He's a real nice fellow and can advise you. Tell him Ron Ellis referred you.
He has some small air tanks, too. We used to stick the tank in the canopy like you suggested or even the wing. They also have a little switch valve you can activate with a micro-servo. It was not unheard-of to put the tank, switch valve, servo and inlet valve all in the wing center section and have tubing connectors to the nose gear.