Jameco (
http://www.jameco.com) has what you want - more powerful than the old Elpac, too.
Jameco Part #174861CB or #174879CB, depending on whether you want a 2.1mm or 2.5mm plug, respectively. Both are 24VDC, linear, regulated walwarts at 500ma. The old Elpac was only 300ma, and is no longer made.
I have one, but haven't tried it out yet (need to build a lot) except to measure the voltage - 23.84 volts, no load. I actually got it to power/charge a PIMETA and batteries, but I will definitely try it on the Millett, too.
Jameco is a great place, by the way - same as Mouser/DigiKey with a little less stuff, but a detailed, full-color catalog. They
do carry some important things like BUF634's.
EDIT:
Oops! Forgot to say that both walwarts are priced at $13.18. another no-brainer for me, at least