Hmm. You know, if all we need is 5V... those usb charger warts that Apple ships with their iPhones and iPads are very nice, and very small, and they seem to last forever (as long as you don't get one of the fake aftermarket knockoffs).
I haven't looked inside to trace where the communication signals get patched back into the power lines, but would it be possible to just remove the power supply circutry that's in there and replace it with one of those warts? I think they're about the same size as the transformer in there.... any other voltages generated by the current PS? Anyone know what the current draw is on the 5V rail?
Just a thought. The engineering Apple (and others) have done on those small warts is superb, and it'd be great to leverage it for something as important as the PLM. I've had to repair old Gb switches (that I didn't want to replace) with crappy PS units, and I've had good luck just finding a contemporary PS that generates the right voltages, can supply more than the rated current, and fits within the case. Newer isn't always better, but from the right manufacturer with the right philosophy, it almost always is. For these PLMs, I'd contemplate something that didn't fit within the original cover and just 3d printing a tumor-like mesh cover to keep fingers from shorting things unintentionally.
Unfortunately, such fix wouldn't generally work with other devices that have to fit within a typical electrical box...