Someone on here my know, Im thinkin Gary RV Wizard, but If you call American Coach and ask them they will be happy to give you the info on who made them and possible how to get to the bulb. They have a massive amount of info on your coach, you just have to ask.
you need a electrical diagram of the coach, they have it.
just about anything you can think of they can likely help you with and you will be treated like you just bought a brand new coach from them.