The first problem is that all of the windows I found were 24 inches wide. This is a real issue when you have a shed with studs set on 24-inch centers.
This is where my Ryobi cordless reciprocating saw came in handy. I gut out a section of the stud, and then braced the stud with another on the outside, so that I had a 24″ wide opening.
I need to trim the window with some 1×3 pine, and we will be good to go. Now I have light on the inside, at least during daylight hours.
Next step is to complete the shelves.