Or you can do what I did.  Go to your local fire extinguisher service/refill place, and check for one of their reject bottles that is about 1 1/2 quarts.  These are lightweight aluminum bottles, usually painted red.  On mine I was able to just peel the paint off, no paint remover required.  I bought a cap neck from one of the on-line specialty shops, and took it to my favorite aluminum welder for welding on to the bottle.  Result is a nice lightweight tank that was the right configuration for me (see photo).  Also installed a low-level switch.

 

Al

Great work on that layout and TIG welding. I use the expended extinguisher bottles for catch tanks. Easy welding and amazingly light.

 

Lynn E. Hanover