Jerry,
Sure, I can help.
I just dug a bit and found the receipt. Looking at the usplastics.com page, I ordered
Item No.: 45354. It's on their page for $84.91.
As for the size, the one I have is 32x48". (basically 1/3 of a 4x8' sheet).
When I bought, it was cheaper to buy a full sheet (and figuring I'd mess up my first try, so I'd have a spare or 2). But, shipping the full sheet wasn't going to be easy. I had them cut it in 1/3's ($10 cutting fee) and then they could mail UPS. So, I have 2 more identical size pieces sitting around. I can part with one or both of the pieces if you're interested (and not in a super hurry since I couldn't mail until at least next week).
For bending, I used a heat gun. I believe I was set on 1000 degrees but found it better to be patient and use 750 degrees to avoid burning the surface. I "think" I made an initial, slight bend off the RTV to get in the ballpark of forming to the ROPS. I "think" I then mounted it using the U-clamps and then re-heated in the areas it was binding.
For mounting, I just used 1 7/8" or 2" (I'm thinking the latter) muffler clamps. I might have some new ones laying around as well if you want those as well. As pictured, the bolts extend out past the nuts some. This can be fixed by putting washers if/as needed just above the new plastic.
Although I did it by myself, it'll be much easier if you have someone else help in the process. E.g. Try keeping the clamps in place (from above the RTV) while inserting the ceiling panel and putting the nuts on (from inside the RTV).
A couple other things.
Note that there will be gaps all the way around (it doesn't reach all the way out to the existing roof). For my particular need, I wanted this so air could get to the amp that's mounted between the roof and ceiling panel. (Also, due to cutting the 4x8' sheet into 3 equal pieces).
What kind of electrical needs will you have up there? I can provide details on what/how I got ele. up there if you want. A couple disconnects, fuses... are handy. I may actually have wire, fuses... as well.
Send me a PM with your e-mail address if you're interested in purchasing the plastic and/or anything else. See what USPlastics wants for the size you want (including cutting and shipping). I'll beat their price (so long as 32x48" works for you). I'll confirm but the 2 pieces I have should be like new. I have taken them out of the box a couple times so I'll check for any scratches or whatever before selling but otherwise, they're still in the box that was used to ship them to me.
Brian