Old standby always works...
If you are still looking...
Don't forget the venerable ATI Remote Wonder and Remote Wonder II
These both work with the included ATI dongle and do not require an ATI graphics card to be installed. They also work without a line of site, unlike an IR remote, which is preferable in a automotive environment. With or without Girder, this remote can do it all fairly handily.
For an easier to operate remote, check out any number of PowerPoint or Media remotes that are out there... say