Does anybody have a list of callers ( and ideally musicians too ) who can stand in in an emergency?

I did a barn dance on Saturday evening having been phoned up by an organiser on Saturday morning in a state of panic as their caller was in hospital; all the tickets had been sold and the food organised. We agreed to do it for the price negotiated - somewhat less than we usually charge but we usually go out with a full band. They raised a goodly amount for their charity.

It made me think that our band would have problems if I lost my voice as none of the others in the band call. I have only ever called for my band and we get most of our work by word of mouth, so I don't really know other callers.

I'm in Kent and we only do North Kent. Does anybody have such a list already? What do other bands do in such circumstances?
FloraG.