Measurement outer window frame window above stove

[JohnM]

We have a 2005 Fleetwood Heritage 640ES, we have lost the widow glass above the stove/kitchen area, the outside window frame measures 846mmx481mm. Can any one help us with identifying the lost window sheave, the window on the outside has a set of makers specification/part number etched on the outside of the glass.
And any idea where we could buy a replacement would be great , but the main thing is the get the window spec from the window glass.