I have a device (Alphasmart Dana) that requires Palm OS HotSync manager, but it's no longer supported by 10.6.
The only thing that I have been able to come arcorss, besides confirming your issue, is the software mentioned in that KB articled linked there. The Missing Sync, no, it is not free, however, it is designed to sync up the Palm OS to the Macintosh computer, even to version 10.6.
iSync, built into Mac, unfortunately will not do it without the Palm Desktop, and the latest versions of both the desktop and hotsync manager just are not going to work with 10.6.
Wish i could give you better news, but that is all I have been able to find thus far.
try syncmate - it is apparently a free alternative to the missing sync. Unfortunately, I don't have that phone or OSX to try it out on, but it's worth a shot, I think