If you are looking for stories and humor in a specific industry, you must work a little harder than you would have to find general humor. Certain professions like medicine and law have many individual books, newsletters, and articles written about them. But if you are a plumbing executive, or you are speaking to the plumbing industry it is unlikely you could go down to your local public bookstore and find a plumbing joke book.
Start a file right away for industry-specific information you find. A good place to start looking for information to fill this file would be in a trade journal for the specific industry. Almost every industry you can imagine has one or more associated trade journals. If you're looking for humor, sift through back issues to find humor you can use now. Virtually no one remembers cartoons and jokes more than a month or so. Watch for industry newsletters so you can extract usable material. Check company bulletin boards regularly for funny signs and postings.
Call others in the industry to look for stories or incidents that would be of interest to your audience (remember to give credit). Collect everything you can collect that is interesting and industry specific and soon you will have the best collection around. Don't forget our friend the Internet. Anytime I need humor on something really specific, I simply type the keywords (ex. plumbing humor, or water humor) into one or more of the major search engines. Something is bound to come up. You must be ready to do some sifting though before you find some usable material. Here are just some of the lines I came up with for the plumbing engineer group I was speaking to. Note: these are the people who figure out how much water it takes to flush a toilet hahaha
My wife's an earth sign. I'm a water sign. Together we make mud. - - Rodney Dangerfield
The shower is the greatest invention. I don't like to take a bath. I don't like to wash my face in the water I've been sitting in.-- Lewis Grizzard
How come when you mix water and flour together you get glue ... and then you add eggs and sugar and you get cake? Where does the glue go?-- Rita Rudner
Getting married is a lot like getting into a tub of hot water. After you get used to it, it ain't so hot. -- Minnie Pearl