Bob,
There does appear to have been some work done on developing a bootloader for SH3-based Windows CE 2.0 machines. I've found some information at the following links:
http://www.tcos.org/Bulletin/current/CE.html
-- Site has a great deal of information, but no time frame as to when the project was being worked on. Avoid the link near the bottom to a LinuxSH3 page at SJB.net, as the site's gone, and goes to a spam page, in essence. Also, LinuxCE.org appears to be gone, as is the SH3-related AOL page. The GTE page was locked when I tried it - it might be locked temporarily, but I have no way of knowing.
http://netbsd.org/Ports/sh3/faq.html
-- Not actually Linux, but NetBSD, and it looks more like talk of development, than an established version.
http://mail-index.netbsd.org/port-sh3/2005/03/08/0003.html
-- Discussion regarding a CE 2.0 bootloader, which appears to not be running correctly on an Ericcson MC16. Might be useful to talk to the developer, though, who's one of the participants.
http://handhelds.org/archive/linuxce-faq.html
-- A copy of the old Linux CE project FAQ. Hate to say it, but it's looking pretty abandoned.
Also, have you checked www.handhelds.org ? Someone over there might be able to point you in the right direction.
Let me know if you have any success - I'd like to try something similar with my 360LX.