Extended fuel tank on a Champion 3100 generator?

I need to figure out a way to hook up a external fuel tank to extend the hours I get out of my generator. I know the Champion 3100 is a gravity fed system and also know of a company that makes a kit which would cost me $300 to install but is there a way to set up a system utilizing another tank that is elevated above the generator to use instead of utilizing an axillary fuel pump to do the job. Don't want to spend $300 if I don't have too. If so please share with me. Thanks guys!