Another possibility is to use a 35 mm film cannister. There is a shoe repair glue called 'Goop" which you can use to seal the holes for tubes. Annother possibility is to use a small balloon. Attach it to the fuel line (twisty tie or rubber band) with some fuel line inside with a couple of notches cut in it. You fill the baloon with a syringe through the fuel line, then suck all the air out. Leave the baloon soft. You can put the balloon inside the film cannister, or use the cannister as a tank directly.