hardwire it to the power supply in the computer.
use the 5v and ground pins from the power supply, it will be switched on and off just like the ps/2 port, plus it will leave the ps/2 open for whatever you want to put on there.
the data isnt going through the ps/2, all you need is the power.
well.. thats my idea. if you dont want to cut the cord, pick up a ps/2 cable at the store, cut the end and use the wire to tap the power supply, and thne you have the right kind of connection on the other end.