If I recall correctly, the Series 3, Series 3c and Series 3mx are the only PDAs that use the Psion SSD cards. I'm not aware of any other PDAs that uses these.

If you're comfy with the Psion brand, you may want to think about a Psion 5MX - it won't accept SSD, but it's easy to convert data using the PC PsiWin package. The 5mx has been out of production for 8 years, but can be found on eBay.

Failing that, see http://www.filesaveas.com/pdaconvert.html for help on getting Psion data converted to something that can be read on a PC and/or transferred to a different portable device.