I have just the unit for you. Unfortunately it's inaccessible due to its size and weight and the fact that I am in California.
It's a Dressen-Barnes 62-117 boat anchor tube supply with voltage and current meters and regulated outputs of 0 - 300 V at 200 mA and 0 - 500 V at 300 mA. The two outputs can be put in series, yielding 0 - 800 V at 200 mA. There is also a variable ac for heaters. No current limiting. Runs from 120 V 60 Hz.
It's very old, perhaps 50 or more years but seems to work.
Will cost a fortune to ship.