Some ideas:
-Call the University of St. Louis golf coach, find out a few teachers his players use.
-Ask the pros at the courses you play where they get/would get lessons besides themselves.
-Find out who the best playing pros are in your section. Although not always the case, it is easier to trust a top player rather some guy that took 8 tries to pass his PAT.
Here is a good place to find out who plays well in your PGA section