You might try Upscale Audio as they rep Manley gear and they also sell tubes.
Think the early Stingray amps came with EI (Yugoslavia) EL84's.
They have not been produced for years, but Upscale has them in stock.
I used the EI's in a Pilot 232 power amp and a single ended Magnavox amp with good results (sound was similar to Philips/Holland EL84's).
I also used old Russian 7189 types (later marketed by Sovtek as the EL84M).
They were not as 3D, but I still liked them in the Pilot.
However, the Pilot uses gobs of negative feedback (unlike the Stingray).
Maybe old production Amerex/Holland if they want to splurge on the input tubes.
Not familiar with the driver tubes.