You *have* to get an additional server running Server 2003 (or later), no way around it.
SBS (for good reason) does NOT support Terminal Services in Application Mode, full stop.
If the new TS is W2k3, you can install the Terminal Server License on your SBS; if it's a W2k8, you'll have to install i ton the TS itself.
In addition, you will need TS CALs. Unlike Windows 2000, *all* devices/users accessing a W2k3 terminal server require a TS CAL.
The Ultimate Guide to Windows 2003 Terminal Server Licensing
http://www.brianmadden.com/blogs/brianmadden/archive/2004/04/01/the-ultimate-guide-to-windows-2003-terminal-server-licensing.aspx