Kai,
I would engage your local Extreme partner or Extreme sales team.
You could use our Extreme Wireless WiNG WLAN product line, which supports both Mesh/bridging and client bridge on some AP's (I'm not super familiar with Client Bridge).It sounds like you want to do Mesh.
You could also use the Extreme Wireless line to do Mesh as well, which would require (minimum) a controller, and at least one AP to act as the root AP and one to be the client/bridge.
With either solution (and any other vendor in general), you will want to have a single vendor provide your WLAN in that location. Roaming between different vendor AP's is generally going to be problematic.
Good Luck,
Ryan