Not sure what you mean, except possibly wall trough planters - these are usually metal, in strips, with a fixing at the back for screwing to walls. They need lining with moss or similar before planting up - most good garden centres will have a selection

I would also say a garden ceneter or hardware store that has a garden section. I think that they come with a plastic container that drops into the metal frame.

or have a look on the'net, also some craft worshops have them for sale, or will make them for you

If all else fails:

http://www.kinsmangarden.com/