FYI, the newest Palm OS 5.x-based Tungsten palms DO support serial comms, it's just that the serial is TTY level and not RS232.  These Palms and others that have the "Multi-connector":

https://en.wikipedia.org/wiki/Palm_Multi-Connector

These can hotsync via serial, but you will need a TTY to RS232 level converter in the cable.

Older  OS 5.x units with the "Universal-connector" have true RS232 signals and will work also.

https://en.wikipedia.org/wiki/Palm_Universal_Connector

Also, there were some USB only palms like the Zire 72, but even those have bluethooth support and could do serial syncing via a bluethooth to serial adapter.  

All these Palm can hotsync via IR also, and there are IR to serial adapters out there.  

HTH,

Rick