Another good source for a vacuum reservoir tank is an empty Freon drum. HVAC shops will probably give you all of them you're willing to haul away, since most of them aren't refillable. They come in various sizes, and some of the smaller ones will tuck inside a big bolt frame channel pretty nicely- - - -maybe more than one in tandem with each other.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!