stone top cap for retaining wall

Here is what my project is:

The customer is having a retaining wall built for their home along the river. Part of the wall will be next to the river and (http://maplered.com) then come up to their home. The center of the wall is 8" of concrete. On the outsides of the wall they will be using brick that matches the home. So the wall thickness will be 16". What I am looking for is a top cap to go on top of that wall, with a little overhang so I'd like it to be at least 18" in width. The brick is a beige or tannish color. This wall will be next to their patio/pool area so they want it to look nice, also, people may want to sit on it.

I'm not sure where to look to find this kind of top cap for a retaining wall. I've called many places (concrete business's, retaining wall builders, etc) most of them have top caps, but they would just be a plain cement (not pretty enough), or nicer top caps, but not large enough. The price is not really an issue, they just want something pleasing to the eye and (http://maplered.com) that goes nicely with the brick from their home.

Thank you for any help,
Lynn M.