Thanks for your continued patience, both of you!
I think my best option is to get a 12v SLA, charge it with one of these multi-output-voltage PSUs, and use the SLA to power the camera, with a DC/DC regulator to step it down to 8~9v. I'm assuming that the SLA will not mind a cheap-and-cheerful PSU which is noisy and which is likely to go above 12v from time to time. (I'm going to buy meself a new multimeter, BTW -- haven't the courage to face the loft!)
This is probably a case of a little learning being dangerous, though. I don't have the technical confidence to know whether what I'm proposing is sensible, or the know-how to measure whether anything I come up with is sensible -- that's why I came to this forum for help.
I think my best option is to get a 12v SLA, charge it with one of these multi-output-voltage PSUs, and use the SLA to power the camera, with a DC/DC regulator to step it down to 8~9v. I'm assuming that the SLA will not mind a cheap-and-cheerful PSU which is noisy and which is likely to go above 12v from time to time. (I'm going to buy meself a new multimeter, BTW -- haven't the courage to face the loft!)
This is probably a case of a little learning being dangerous, though. I don't have the technical confidence to know whether what I'm proposing is sensible, or the know-how to measure whether anything I come up with is sensible -- that's why I came to this forum for help.