[LazyPup]

This may be a real longshot but I can think of one possibility. Hopefully you have a zone valve to the shower, if not you will have to turn the water off at the main. Remove one of the valve stems and take it to the store. By matching your stem to a new one they should be able to narrow down your search to the manufacturer and possibly the model or type. Once the manufactured is known it should not be difficult to locate trim escucheons to fit your mixer or replacement handles that will fit your stem.