Small Multiplexor - cheap

I need to monitor the temperature across a large surface area and have
a method divised already on how to do it with individual isolated
sensors. However, I only want to run one set of leads back to my
accquisition system. Is there a good source for a small multiplexor
that would just relay the the current being passed through it, polling
each sensor?

Cheap and small (microprocessor size) is definately a plus.


Thanks-

David