Build your own!!
Thats what I'm going to do. I found a heavy CAT dozer tank in the dumpster. It sat on the ground and got a big mouse nest in it. (The filler hole is about 6" around) But it fits exactly in the bed width wise and goes up about an inch over the rear window and tapers toward the rear like a wedge.
I am going to cut a big piece out of the top, send it out for strip and derust, and replace the top andput in dual filler openings. Can't wait to get started on it!
Oh, if you want to make nice hoses or lines for anything. I use aeroquip braided stainless with the anodized AN fittings. Very strong and looks great too. Very easy to make custom hoses this way, no special tools needed and the hose ends are replaceable.