JimP: Spoke to Brad earlier about the power supply and he said the what works for the LISA II ( Pocket Reference II) should also work for LISA III.
I have a PSR for PRII and would expect it to work, though the charging rate may be slow for the Expedition.
Before I get the PSR I was using a PSU which I bought online from RS Online http://www.rshongkong.com This is an often overlooked resources for guys in Hong Kong who look for good quality hardware and can't find them at Sham Shui Po.
Do a search for item item 423-7880 or 423-9252. Both versions work for my PRII and they comes with different tips so fitting the LISA III should be no problem. The 423-9252 is better because (a) it is a Germany AN-MANN design, and (b) it has selected outage voltage so that you can have a little bit of safety margin by setting it to 22V instead of 24V).
I can lend you the 432-7880 if you so wish for your immediate use with the LISA XP.