Switch port lock?

[Travis Roy]

Does anybody know if such a device exists?

Something that can go over the front of a switch that can lock the ports 
with or without something connected to it?

Of course the ideal method would be to have all the switches in a 
lockable space, but that's not always possible.

I'm just looking for something to stop customers from moving their 
switch ports and/or unplugging or plugging in cables without us knowing.