Same problem. I've searched the web, camping world, etc, and several local glass shops/home dep/lowes, etc. to no avail. Called my dealer, and they said will order one from Keystone. At my age, may not live long enough to get it, but looks like thats the only option. If you get a response to your request, let me know!
2014 Montana Mountaineer 331 RLT. Winneguard SWM Traveler Satellite Antenna, Progressive 50 amp portable EMS, 6 point Level Up.. 2016 Chevy 3500 Duramax Dually, long bed, B&W Patriot hitch.