NEB sells several Phage Display libraries. Some have 7 random positions and others have as many as 12 random positions.

commercially those libraries are available but depends on you that what sequence you would like to have. those DNA libraries are having random sequence not specific . people mostly use those random libraries for aptamer selection. there are many companies which are having those kind of libraries in research market.

Thanks for your answers. Jack, I'll look into the Phage display. Ajeet, can you provide a specific example (or examples) of a DNA-encoded chemical library that is commercially available? I don't really care what the sequence is, as long as each compound has a unique and known DNA sequence associated with it.