Just give him the vendor info. You are not a var/reseller/rep, so you are not supposed to be making money from referrals anyway. One of the golden rules of good business is: only charge people for exercising your profession. If you do some little piece of work that is not your regular business, then it is a favor.
In my experience an area where small business owners frequently make errors. They do something that is out of their bailiwick and then wonder, "How do I charge the guy for this?" It's one of the oldest principles of business and goes back to medieval times: Don't do stuff that you are not in the business of doing, and if you do do stuff you are not in the business of doing, don't try to charge for it. It's a favor. If a doctor stops to give a stranded driver a jump, he doesn't try to charge the guy $400 for using up 30 minutes of his time. That's because he's a doctor, not Triple AAA. He is not in the business of giving roadside assistance, so if he does, then it's a favor.
As for material markups: DON'T DO IT. It's sleazy and unbusiness-like. Are you a steel dealer? No, you are a machinist. Trying to hide profits in "shipping and handling" and material markups and things like that is unprofessional plain and simple. I used to know an executive at Princess House, a company that sold "collectible" dinnerware and memorabilia. He bragged to me that the most profitable department of the company was "shipping and handling". He thought they were being shrewd, but they were just being dumb. Princess House is defunct now and their products are as worthless as their business model was.
Real businessmen charge for their business and nothing else.