Personal Java is just a spec. It's not geared towards an OS, its Java!
There are some other vendors that make PersonalJava VM's for WinCe, of particular note Jeode, which makes one for Ipaq. Their runtime costs like $20.
This link provides some useful info:
http://www.javaworld.com/javaworld/jw-10-2001/jw-1026-devices.html#sidebar
-Brad