So I'm having an issue with my truck where the air is stuck on the defrost. One morning I found a strange piece on my floor on the drivers side which now I believe to be I guess you would call it a horn for the actuator you speak of under the steering wheel. So that one I believe is the defrost actuator.

 

Welcome to the forum Mitch. I moved this into a new thread.

What year is your truck? '01 and up are electrically actuated. Earlier years are vacuum operated.

As to that piece you found, you're probably going to have to check a boneyard. Many small parts are now discontinued.

 

also check ebay for small parts. I have found numerous discontinued parts there.