I assume you have an Audio Research LS25. I still have an LS25 mk2. I know there are no replacement remotes for this model. I talked to the Audio Research rep about remotes last month at a party for the G series. Though I was more interested in being able to use just one remote instead of the 5 Audio Research remotes I now have. He told me that they are considering making a universal remote that would work with all Audio Research equipment.
At least the preamp remotes are model specific. My LS27 remote will not work with my LS25, the functions are all different from the keys.