I just found another great site in Germany:
in which he redesigned the dc-dc converter board inside the BP-8
with surface-mount components, and even sells them... for $25 plus
$12 postage :(
To be fari, I don't think that's very expensive for what must be a
small-volume product. I've done a fair numner of 1-off designs, and gave
up trying to sell them when I realised what a fair price would be...
Guess I'll be using 9V batteries, or perhaps tuck a rechargeable
one (which is really only 8.4 volts) inside the plastic case with
a suitable diode and resistor for charging from the wall-wart.
Or you could redesign the DC-DC converter. It can't be that complicated.
Perhaps one of thestep-up swithcing regulator ICs (Maxim?) would be a