I don't know of a commercial maker of reproduction fuel tanks. There are a few people who have made their own. One example is Gordon Yeo's C8 project
http://www.mapleleafup.net/forums/sh...highlight=tank
Jordan Baker is rebuilding the fuel tank in his Otter. If your problem is pinholes, it is possible to solder the holes (been there). You aren't the first to have faced this - see
http://www.mapleleafup.net/forums/sh...ight=fuel+tank