First let me welcome you to the forum.
Have you contacted your dealer about replacing it or getting a part number or size?
Not knowing the exact specs on your skylight. If you know what you need, a simple google search should give you plenty of choices.
Good luck and Happy camping!
John (USAF Ret) & Cheryl
San Antonio, TX
2014 Hill Country 32FR
2011 Ram 2500 4x4 6.7 CTD