I am looking for some wireless speakers for cold produce storage rooms in a warehouse. What is needed is one transmitter and (5)separate wireless receiver/speakers, with maximum daitance of 300ft. These are for large refridgerated area where customer stores produce, with fairly-thin, insulated aluminum walls. Customer says other companies have this, so the wireless speakers should work through the walls, since they are not steel.

Does anyone know where I might look for these?