Loopback adapter

I had the painter into one of my sites the other
day and they removed and mixed up our face plates
Office cant afford a tone generator so I am looking for a cheap way to identify wall and rack ports

I have thought about creating a rj45 loopback plug
and testing with an ohm meter. I have an idea it
would work but implementing it well thats where i need your help
any suggs or thoughts are appreciated before hand
jim fox