Check out http://www.digitalartsupplies.com/.com in San Diego.
I would check out the sheets of Ultra-Smooth dual sided it is VERY thick and smooth . One
of my students used if for a fianl book and it was actually too thick for a book but it looks
great. I know Nash Editions used it for awhile. Also Arches has a new very thick version of
Infinity I believe and Hahnemuhle has a really thick version of Photo Rag, also in sheets.