OldIHC

Check out one of the local truck shops for a nice air tank that will act as a vacuum tank. Some of the air drier rebuild kits came with and air tank that was often as not used, so they tend to collect dust in the parts department. I got several of them for free because I asked. Picture later. Maybe you could repurpose a fire extinguisher for a vacuum tank. Check with your local fire supply store. They may have some "tanks" that have past their best before date. Even an empty propane hand held propane tank would work with a modified control valve. You might want to take out the SCHRADER valve in the top. Use a little caution. Propane can burn very quickly and depending on the speed of the combustion, it may qualify as an explosion. Your auto wrecker will have nicely formed vacuum tanks in a variety of shapes. The manufacturers like to hide the tanks, so the shape may change and some of them look interesting.
I see my toes, but Mr. Happy, not so much. Does that qualify me for chubby plus?

as long as someones happy, who cares if you can see him?

An old school bus (or truck 70's up) with hydraulic brakes and hydro-vac will have 2 vacuum reservoir tanks (required) make doesn't matter,they all had them. IIRC the ones on a Loadstar were about 6"D x 20"L.