Now that you’ve built it, most of those parts, even the 3-way valve,
are available at better hardware stores. In California, OSH used to
stock them before the beancounters gutted the place. (Sorry) (They
even had vacuum gages.)
Meanwhile, might I make a suggestion? In the detail picture, it
looks like your trap is a glass bottle. It might be safer and more
efficient to replace that with a trap built out of a short section
of black iron gas pipe. I did that to the vacucast out at school.
(The new ones don’t come with a trap anymore, so you’re stuck
rebuilding a brand new machine, just to get it up to spec. Right
out of the box. Gurr…) The reason I suggest replacing it is: hot
metal plus cold glass equals broken glass and hot metal all over the
guts of your machine. Annoying and possibly very expensive. With the
black iron pipe version, you just unscrew the bottom, pull the slug
of metal, screw the end back on, and you’re back in business.