We were looking for one of those recently, too. Until our last campground, we've always had fairly level spots, and the standard step on our 181 was just fine. We were at Hot Springs, and had a site that sloped down from the road, so the tongue was almost on the ground and the tail was up in the air. Naturally Wal-Mart didn't have anything to help and the nearest Camping World was some distance away. I'm sure there probably was an RV dealer in Hot Springs, but we didn't take the time to look.
A mid-door has an advantage on a sloping site since it is likely to be pretty much at design height no matter what.