Hey, I know that THULE makes or made a roof rack with fit kit for the sunroof equipped Previas- which was good for up to 165 lbs. Check their website. I'm not sure if they still make them but I believe that they do. Also, consider looking on e-bay for roof rack systems. There are very few small companies that might make racks for moonroof-equipped Previas, but THULE is he only big name brand that does. On another note, OEM aftermarket racks are a rip off. They are usually left over stock from big name companieslike THULE, YAKIMA, SARIS,TERZO, etc. When those companies redesign thir equipment, they sell their left over old stock to auto manufacturers many times. The manufacturers, put their names on them and sell them as OEM parts (Ford, Honda, GM, Toyota, GM, Isuzu, VW, BMW, Audi, Dodge, and Nissan come to mind.)
Also, about the Hot/Cool Box- been looking for one for a couple of years now. I've never seen one on a US-spec Previa but the Canadians have them. According to my sources at Toyota, it was never offered here in the US. I want one and I asked a few dealers about them. They told me that if I did get one, I'd have to get the pipng as well and who knows what type of condition the piping will be in on a Canadian donor Previa. Canadian models tend to have rust and the labor to install them isn't cheap- unless you do it yourself. I've also been told that it drains quite a bit of power also. I don't believe all of this being that I used to own an '89 Toyota LE Van with dual sunroofs that had the icemaker/refrigerator- which is pretty much the same as the Cool Box. It worked like a charm and it didn't seem to drain any more power than it already did with the A/C on. In fact, living here in So. California alone should've warranted offering this feature. Toyota, there is a market for the Cool Box here in the States. Are you listening?