The cheaper the better since you will be using it for this simple task. I only know of one and I think it sells for around $90.00. It's the Universal Remote SL-9000. You might just try running a "WANTED" thread on the Pronto forum and see if anyone will sell you there old remote. One thing you might want to look into if you do decide to go this route is add more than just that IR function. There is several X-10 relay boxes that would allow multiple contacts to the remote. This could allow a RF X-10 remote in the bedroom the ability to turn off the A/V system. I use to take remotes apart in car audio systems and use a multi-function car alarm remote to control features like volume, track adjust and pause from 100's of feet away (wanna see some peoples head turn when a car starts, rolls down the windows and cranks up the stereo by it's self). Anyway, this is not new to me and is very simple. You can use flat multi-conductor computer cable to do the connections. This cable allows you minimum cutting of the remote for the wires to exit. If you decide to do it, keep me informed of how it works.
