We did the plexi-glass thing too. You can get the plexi-glass at Lowes/Home Depot usually. They may even cut it for you or you can cut it on a table saw.
For the life of me, I do not understand RV manufacturers putting wallpaper OR mirrors behind a stove or sink!!!!!! Ours had the mirrors. Yeah, like I need to see what I'm cooking in a mirror!!!! They say it makes an RV look bigger ------ it may LOOK bigger but it doesn't mean the RV can hold more stuff!!!!! The rig is x by x and looking at a reflection in a mirror won't make it hold more!!! (okay, I'm ranting)..