With HotkeyNet, you can make a cheap external number pad work like an X-Keys, provided you have more than one PC.

You plug the number pad into one of your remote PCs (not the main one) and load a script on that remote PC to remap the number pad. The reason this works is that with HotkeyNet, every PC (not just the server) can load scripts and control all of the PCs, and each PC can have a different script.