Why not use a couple of Eveready 415 45 volt
batteries? They're
still made, the last I checked. Service life should be shelf life.
Ease of getting them. O can get 9V (PP3/006P/6F22/whatever they're called
this week) batteries almost anywhere. I don't know a UK supplier for
45V batteries (even the 22.5V ones [1] are getting hard to find). I
don't fancy gettign a couple of batteries shipped acorss the Pond every
time I need them
]1] Called 'Photoflash' or 'Hearing Aid' batteries in the old books. The
fomrer because they were used to charage a capacitor of About 100uF to
fire the old single-shot flash bulbs. The latter becuase they were used
to provide the HT+ (B+) voltage for valved hearing aids.
-tony