Does any know an aquaculture facility to purchase either (stonecats or margined madtoms) from?

Also, for those of you that have caught them to use as bait, what methods have you used to catch them?

None that I know of...

Seining and minnow traps have been my best methods. Most streams or rivers with a madtom population will yield good numbers by baiting a minnow trap with slightly rancid liver or another stinky bait that is left over night.