One suggestion would be a gravity fed tank above the level of the toilet tank. Then ya just gotta get the water up in there... which may be higher than where you got the big storage tank... Come Back Heath Robinson, all is forgiven...

I'd suggest hiring Paris Hilton with a bucket... depending on who ya got staying in the van... I been thinking of visiting you...

This saga is starting to suggest a song about Bobert's friends helping him, along the lines of a cross between "That's What Friends Are For, Boys" and "Right Said Fred"...