3M #4460 will probably work for a typical 25 pair shielded cable to clamp onto the outer jacket's sheath. It can be used for much smaller cables by spreading the cable sheath open to allow it to be inserted between the cable core and the sheath.
The 4460 is also known as the "gator" clamp. Here is a link to the 3M bond clamp page:
Check this out Any wholesale supplier should have these clamps, such as Graybar, Anixter, CSC, etc.
I am assuming that you are working with standard outside plant cable. When you mentioned "CAT 3" cable, I doubt that this is what you are using. It sounds as if you are using indoor cable that is shielded with a standard drain wire. If this is the case, then just collect all of the drain wires and terminate them at a common termination point.