http://www.kloterfarms.com/page.cfm?p=1
They deliver nationwide. But it looks like Maryland is just out of free delivery range.
I have one of their one-car garages. The previous owner of the house i just bought got it, so it's a few years old. I don't know how much it cost and can't find an exact match for mine on their website. Mine looks like a "cape" style.
I can tell you that it's well built. It has a plywood floor supported by joists, like a shed. Exposed studs with no insulation on the walls. It also has an asphalt shingled roof.
It's sitting on a bed of golfball sized rocks. I don't know if the previous owner, or the company prepared the site. Also, there is a solidly built ramp leading from the ground to the garage floor. I would park a car in it, but would not work on it because I wouldn't trust the floor to support the weight of the car on a jack.
I do hate that it's not a concrete floor. Also, that they didn't have electricity run out to it (it's about twenty feet from the house).
There may even be a company like this closer to you, since you're closer to Amish country.