Replacemant windows

I unfortunately did the rear window of my motorhome a mischifef recently and require a replacement. Can any member assist with tracing a double glazed plastic window for  2005 Auto-Sleepers Nuevo, the size required 38 1/8" x 21" or for thiose who prefer metric 97 cm x 53 1/2 cm. Any help would be gratefully appreciated Auto Sleepers can only supply the complete window including frame in the wrong colour at an excessive price