Jim,
You can take the DOT number off of the lens and match it up with a replacement at most large truck part replacement shops. You can also buy them on line. There are several options with replacement lights that you will have to decide. You can use LED lights or incandescent lights. The incandescent lights come in either the standard plastic lens that the coach was originally equipped with that is readily available or polycarbonate lens that is much better but hard to find.
If you want to just make one call and have the lights sent to you, give Beaver Coach Sales a call, because they know the right lights to fit your coach and they have them in stock.
Gerald