I don't have the measurements but exact replacements are very expensive. The good news is that generic replacements are fine, but they need to:
1. Easy part: Be big enough to cover the cutout with room for the mounting screws. There's a lot of wiggle room here.
2. Hard Part: Have a vertical profile that's adequate to accommodate the top of the inner skylight. This is key since many generic skylights are too shallow. It's not just the height but how steep the slope of the sides are. You'll need to carefully measure this with the outer skylight removed and the inner skylight in place. If I recall correctly, this was a limiting factor for the generic skylights I found so I gave up and ordered the exact replacement which cost something like $350 in 2017/18.
The translucent inside skylight makes everything look great from inside and protects the edges of the cutout from shower moisture.
When I replaced mine on my 2002 Suncruiser 35U (same as Adventurer), I had to repair some of the luan around the edges of the cutout that was
coming delaminated due to leakage.
If I had it to do over, I probably would have just repaired my skylight. With the inner skylight in place, you'll only see the repair when you're on the roof. This, of course, depends on the extent of the damage. Eternabond tape would probably work for most cracks.
This IRV2 thread may help:
https://www.irv2.com/forums/f101/200...ns-618497.html