[Milsurplus] 3B28 gas rectifier question

[Laura and Jim]

I found a pair of these and they have continuity on the filaments. 
So............I'd like to use them in a HV PSU (~1kV range) for kicks and am thinking I can't use just any old 2.5V/5A transformer can I? Gotta have high breakdown voltage also because it's part of the HV circuit, correct?

If so, who's a good supplier of these, or have they turned to unobtanium?

Happy New Year!
Cheers!

Jim Falls
K6FWT
Eureka, CA

PS: Am cleaning VC and switch contacts in the TCS for starters. Will report back w/results.