If you coach has Hehr windows, here is a link to some manuals
servicemanuals
Since my coach is at the dealer (80 miles north) I cannot walk outside and verify the window manufacturer.
Here is the link to a window parts supplier. Not sure, but it looks like they have the knob for the Hehr windows. If I am right the part number for the knob is 008-203.
http://www.hehrwindows.net/