I've been putting this off for about 6 months now, but I finally got around to fully dismantelling my SL5500 to find out exactly what FRIED when I accidentally inserted a REVERSED-POLARITY power adapter.
It turns out the the damage was not so easy to spot at first, but in the end, a small hole on the top of a very small component gave the first clue. Luckily the SL5500 has two of these components side by side, so I was able to get the part number off the good one.
The part is an SP6650EU High Efficiency 600mA Synchronous Buck Regulator made by Sipex. The trick now will be finding a vendor that will sell me these in low quantities, or finding another dead zaurus owner willing to be an organ transplant donor.
I guess there are a few of us out there with this same problem, so maybe we could pool our resources and fix them all at once?