We use the faux wood "cut to width" at Home Depot! You will probably be able to get near your size and have them trimmed. Unless you have some really wierd sizes, you may not have to customize any of them! I vacuum or dust them regularly and then every few years I take them down and wash them in the bathtub with a little bleach and laundry detergent...stand them up on a towel to drain and then wipe them down with a handtowel! We LOVE them!
Barbara the best place I found was Overstock.com for bamboo roman shades. I don't know if they have blinds that long, or in all the widths you need, but it would be worth a try. Their prices were by far better than anywhere else I found on the web or in stores. Most stocked goods are only 68 inches long so that was a big problem too. O carries up to 98 inches long. The hardest part was the looking for the right sizes. What I do there is find the style I want then search using it's "name" to find all the sizes. Once I found a size I wanted I opened it in a different tab so I wouldn't lose it.
Thanks for the answers, but I'm still hoping for more ideas.