While I do not own one and there for I am not sure what shape it is (square, rectangle, etc) I would make a cover out of 1/2" Baltic Birch plywood (finish however you would like) to cover the hole and replace it with any car stereo unit you find that gives the features you want.
They will be cheeper/better than buying a replacement from Camping World as well.
As long as it operates with 12 volts you will be fine. You could use consumer electronics for your home but you would then require 120 volts to use it or an inverter hooked up to your battery.
These are just suggestions to replace what is normaly found in our RV's.