Okay, this is probably somewhat of a long shot but I'm looking for the parent tube of the pentode in a 6LU8 or 6LR8 (identical except base/pinout) tubes or their 16/21V filament counterparts. I don't care if it's Compactron, Novar or just plain jane octal. Datasheet included for reference. The 6LU/LR have a triode, I don't care about that and may end up using a second one but I'd rather not have any extraneous sections I'm paying to heat. I am using this for a regulated power supply, so I don't think that it will make much difference if they're not 100% the same so log as I'm not pushing them to the absolute maximums.
https://frank.pocnet.net/sheets/107/6/6LU8.pdf
https://frank.pocnet.net/sheets/107/6/6LU8.pdf