I bought a couple of "Postwoodworking" sheds through a local dealer. They have dealers all over the state. It's well built and has stood the test of time thus far. They will pretty much build anything you want. They even matched the siding on my house. I do recommend putting your shed on a concrete slab. Here's a link to their web site where you can do a local dealer search...
http://www.postwoodworking.com/vinyl-sheds.asp
Good Luck!
Dan