P.S. - I
don't mind the concept of a DC-DC converter, but I'm not
skilled enough to design one, just skilled enough to build it.
You don't have to build one. They are available as sealed
"modules" with pins for gazinta and gazouta; very easy to
use.
Three-terminal switcher modules intended to replace three-terminal
regulators are fairly expensive, around $11 and up in small quantities.
Digikey has some made by TI, page 416 of catalog T023 (Sept-Dec 2002).
If anyone wants an isolated 5V to 9V converter, I've got a huge pile
of them. I use them with a 7805 to get an isolated 5V supply.