I recommend a website for bedding called The Company Store.
I purchased Twin XL primaloft comforters there. They are excellent quality.
For sheets I purchased Twin XL by Wamsutta from Bed Bath and Beyond. Also excellent.
Twin XL is what is used in college dorms, since those beds are standard twin width,but longer than standard. This size fits the AS beds great.
Oh, and just take a pair of scissors to the factory bedding or a basic bedspread , and cut to fit for a mattress topper. Use under the sheets. We did this for our 22 Sport, and just used this also for our 25 twins.