Is there any way (short of having a recording, which I don't) of finding out the corporate sponsors of a show that happened in the past?

In this case, the show was last week. If CBS doesn't issue an apology tonight for last week's show (The Mentalist), I'd like to know which sponsors to write, and to not give my business to, but I can't seem to find out who the sponsors are.

Hmmm... not sure where you can get a list of sponsors other than getting a rebroadcast.
You can voice your displeasure here: The Mentalist Community Message Board - CBS.com though I expect some strong armed moderation there.

I didn't get involved in the forums, but I did send a letter to CBS.

I read the forums, but it seemed a little too much like arguing about whether Wicca was a valid religion than about how CBS should have done more research before broadcasting stereotypes, false information, and scare tactic messages.

So... since I already expressed displeasure to the station, and sincerely do not expect them to apologize for it, I wanted to know if there was a way to locate the sponsors to continue to push for acknowledgement that the show was wrong--and short of that, to express my vote about it by using the almighty dollar.

I was just so shocked last week that I didn't even think of writing down the names of the sponsors.