Which version of Wireshark supports Remote Interfaces.

which version of WireShark does

The version that's built with a version of libpcap/WinPcap that supports remote interfaces and that's running with a version of libpcap/WinPcap that supports remote interfaces.

and how I get hold of it?

Either 1) run Windows (BootCamp or a virtual machine monitor such as VMware Fusion, Parallels Workstations, or VirtualBox) and run the Windows version or 2) add the support to libpcap yourself, compile libpcap, and then compile Wireshark with that version of libpcap.

(No, there's no easy way. At some point in the future there may be a standard libpcap release with remote capture support, and at some point after that Apple may pick up that release, and at some point the OS X version of Wireshark may be modified to use those capabilities if present.)