alright, alright. instead of adding to the arguments, i'll give you an idea that might work.
you can build your own out of copper and silver solder.
either build a complete tank, which is a little tricky trying to get all the angles perfect, or you could get a piece of copper pipe the size you want, and solder on two end caps (if you're lucky, the same place you got the pipe will have the caps. if not, cut two circles and do it yourself.)
i could build a pipe bomb lookin' tank in about an hour. you could also make a box shape, rectangle, or something similar with sheet copper just as easy.
if you're going to make a custom cover for it, you don't need to make nice pretty joints, you can just slop the solder on and be done with it.
now for the bad news...
copper's not cheap.
let's say you want a 2 foot long pipe tank with a 3" OD. no problem. it's only $76.98 from here;
Copper pipe - rigid copper piping - from FAMOUS PLUMBING SUPPLY
two end caps will cost you $36.71 apiece.
then you need silver solder, which is 10-20 bucks, depending on where ya go and what size you need.
you might want some tank sealer for it, too, just in case...
if you build a box tank, i buy 16g. copper sheets for about 60 bucks. there's enough to do three tanks. or, two tanks and one you can bash with a hammer when you mess up.
i actually looked into building copper behind the seat tanks. figured i just get some 5" OD copper pipe and solder some caps on the end. make 'em about a foot long,take me about an hour each, probably sell them for 50 bucks...
sounds like a good plan, right?
first, i couldn't find 5" od pipe. it's out there, but not too common, so i found 4". that'd work.
and i could get a 4' long piece for
only $299.96!
right there i decided people can stick with their juice can tanks.
but, just to be thorough, i still would need 4 caps and bungs, solder and sealer, plus some way to mount them. going the cheapest route with leather straps and hose fittings, i could probably build a 1' copper tank for a little over a hundred bucks, but maybe as high as $150.
not counting my labor, shipping, etc.
to make a profit, i'd have to sell them for at least 200.
the copper tanks i make out of sheet copper are a lot less to make, but take a day or two, are more prone to leaking, and are a total pain in the ass, but they're getting easier for me.
the bottom line
NOTHING about building a gas tank is cheap, or easy, no matter what it's made out of.
unless you can find a suitable container (like an old aluminum canteen for instance) or a ready-made product you can adapt to your use, you're looking at spending a lot of money, a lot of time, or both.
honestly, it'd be cheaper in the long run to buy a welder and teach yourself how to make the tank you want.
all that being typed, i'm not trying to discourage you at all. just being realistic.
