Bagger:
You won't be able to just buy the mouse and use it with your wireless keyboard reciever. I currently have both sets. The wireless reciever is differnt depending on if you have a wireless mouse with the keyboard. Notice how your Wireless reciever connects to your PS2 port for your keyboard. The wireless mouse/wireless keyboard reciever has two PS2 one for mouse and one for keyboard. So there is no way you could get the receiver to work with your keyboard and mouse at the same time.
Perhaps you could use it one at a time but that might defeat the purpose.