The standard for this application are made by Bilco and they are called bulkhead doors. They come in several sizes but you still might have to do some modifying with pressure treated wood or concrete to fit your opening. The lumber desk of most home centers should be able to order them for you.
We have Menards in the western part of the state and Home Depot and Lowes are the standards in the Detroit area. No Gordon's here but we do have a lot of specialty lumber yards.