lot of surf related pictures but that one blows me away.
4'x8' sheets, but they do custom sizing as well- and can help you lay out the pattern. There would be breaks- but depending on the color and pattern- they are not obvious. Here's a link to their Art Diffusion line: http://interlam-design.com/products/art-diffusion/ .
Surf the web, try typing in lighting, or ceiling lighting. Also try Home Decorators collection, it's a catalog that offers a variety of things, try New York Lighting ( I think that's the name), but there are several places that offer this style of lighting. Checkout Home Depot and Lowes too.