Greetings:  I had the same dilemma last year when I built my vacuum
gauge.  I knew the stuff was available, but could not remember where
I had seen it.

Finally I remembered that the tubing could be purchased in 3-foot or
4-foot lengths from the local tropical fish store.  It is used in fish
tank filters.  It worked great!

Sincerely,

Tom Gregory
Waukesha WI