Depends somewhat on how visible that area is. There are plastic panels with spring-loaded clips that will let you snap it in. If it is a tiled area, www.schluter.com makes a tile-in set of magnets that can hold it in place. You could use a piece of drywall and frame the edges with c-channel to protect the edges, then screw it in place. Lots of choices. You could frame it out and just put a piece of plywood (harder to match with paint to look like drywall).