We have a framed tiled shower built in 1959. It has four sides tiled including a hinged doorway. The tiles in the doorway were falling off, which we were going to repair with silicone. Upon cleaning the area up to replace tiles, we discovered that the doorway wasn't covered with concrete board or the like,it just has 2x4s behind it. Also, more tiles were falling off in the doorway. I can see that behind the other tile is drywall board. When I look at shower wall inserts they only come with 3 sides, what can I do for the front wall short of retiling the whole shower? We will never be able to match the original tile. The whole bathroom has tile halfway up the wall. Is there an easy solution?