I checked in my cd's of Leopard and Snow Leopard but I haven't seen any way to download the isync version for my OSX.
It is not part of the application software installed with the system? You may have to boot to the disc then do a custom installation of the item, or use the shareware Pacifist utility.
I removed the isync by mistake... finally I simply copied it from a previous stored version with time machine.
Retrieving data ...