Branch office VPN

We are currently connecting Neoware thin clients to Windows 2003 Terminal servers. Our firewall is an ISA 2000 Server with the Terminal servers published. We have a branch office that is setup with 3 thin clients connecting via RDP session to the published Terminal servers. We have no VPN setup, only a router and cable modem. We would like to get a networked copier at our remote location but it will not work the way we have it set up. Do we need some type of VPN or PC at the remote location? We would like to stick with all thin clients. Thanks