You are going to find it hard to find a direct replacement for the SmartShed Deluxe skylights... I have had to replace both of mine a couple of times in the past 10 years, as they yellow, cloud and crack over times... I have replaced them with a plastic skylight dome from the following website: http://www.plasticskylight.net/rvskylights.htm
I used the 15" x 15" Clear version with the 18" x 18" OD flange... I took a cutting tool and neatly cut out the old window lense from the skylight frame... then took the new clean lense and used outdoor clear silicone (RTV) caulk and layed a thick-wide bead on the roof surface, then placed the new clear lense in place, then put another thick-wide layer of outdoor clear silicone (RTV) caulk between the original lense frame...then I drilled small holes around the original lense frame to snuggly fit 1 #10 or #12 machine screw long enough to go thru the original lense frame, new clear lens cover and the roof of the shed, so that you can put large flat washers on both sides of the bolts and then a lock washer and matching nut to fasten the parts together...remember to also put some of the Silicone caulk in each of the drilled holes so there is no leaks...also cover the head of the bolts with a thin layer of silicone caulk, as it will keep it from rusting and moving when the skylight and building flex due to wind or temperature changes... Remember to evaluate what you have and what you think with work for you and your abilities... This is a 2-3 person retrofit... One person above, one person holding the ladder and one person inside fastening the bolts, etc...always think safety first...
