I ordered a Lexan Skylight from these guys rather than replace it with another cheap factory acrylic one. Replacement RV Skylights from EZ Tops World Wide Inc.
It was less than $100 including shipping and should hold up better. Installation was straightforward. If you're replacing it anyway, you may consider alternate colors. I chose white to cut down on the heat transmitted through and am thrilled with the results. It lets in zero heat and so much light that I can not really tell a difference from the original.
'04 GMC Sierra 2500HD, CCSB, D/A, MaxBrake, B&W Companion, Retrax Pro, AR Power Steps
2013 Rockwood 8289WS w/Diamond pkg
1969 Camaro RS/SS Convertible
Dad's old 1968 Empi Imp (recently recovered from under 21 years worth of boxes/dust)