When I started planning my fusor, I also wanted to buy a perfect sphere as my first investment. Excellent equipment was also around 6000€ without electro polishing on the inside. I asked at Pfeiffer, Lesker, VACOM and several others delivering to local uni-institutes.
Soon I found out that there are a lot of other challenges which have to be solved before. It took me many weeks to decide if my parts should be made out of aluminum, steel (which steel), or to select the right pressure gauge and mass flow controller. Or the simple decision between ISO-KF and CF and metric or inch based parts.
So I started with the roughing pump, using a glass based construction for the first plasma tests. Then the turbo-pump followed. Now I’m switching to a double-cross (DN100) – which is quite cheap. The HVPS will be the next major thing which is just in production. Isolating 45 kV will be one of the next not so easy tasks.
My hint: Start with the easy parts and select them in a way, that you can reuse most of them later (as base for an ion gun or something else).
It's not about buying stuff, but about learning how to handle the componentens and the different new technologies. Example: Nobody can show you how fast you can vent your Turbo - you have to try. Doing it too fast, might cost you 4k€
Good luck!
Werner
Attached you see one of the first tests (mixed He + air)at 50 kV but only a few µA just to see how isolation works and to get used to HV, radiation and shielding.