Know what you mean David. Bought a welder in part to try and make tanks. Is a bummer finding good ones. I too thought they were crazy expensive but as pointed out, lotta work goes into em.
Today went to a semi local bike shop looking for 12g spokes but they were closed. Any way found a place that makes first-aid, lunch, tool boxes etc. Gonna stop by and see if they or if they could make up some rough ones for me. Bare bones sort of thing and finish them my self. (paint, petcocks and site tube) Dunno. Be kinda cool if the are set up for some thing similar and can make 10 or so up easily. Well, some what cheaply, snork.
This is their link. American Metal Crafters - Metal Boxes & Cases, First Aid Kits & Cabinets and Custom Projects
Really old factory. Kinda becoming a thing with me. Finding and touring them. Have made some great finds.