Word of warning: the Lowe's in Mooresville carried next to nothing compared to the Menards in Camby. If the Mooresville stock is representative of what Lowe's carries in its other stores, do yourself a favor and skip it. We don't have a Home Depot within convenient driving distance (and I don't like it anyway), but you might try there as well.
There are some garden retailers on Green Street just between B'burg and Avon (Frazee's is one, IIRC). THey might have some, but I would call first. Might just be landscaping and not hardscaping. It will probably be more expensive as well.
It's a little drive, and they have odd hours, but go to the stone center. It's off of binford. It's mainly for contractors, but I buy all my stone stuff there. Much, MUCH cheaper than anywhere else.