So I ran across this site a few weeks back. I have to say that I have never ordered anything from them as of yet but, it seems like they have an extensive list of parts. The site is called Truckandcarsparts.com. They are location in Orange California, which is East of the Los Angeles area. The phone number is listed as 800-235-2470.
They show a new El Camino only fuel tank for $129 and the part number is 59-10903. Take a look at there site and let us know if you are successful. BTW. Has anyone else known of this company or ordered anything?