I don't know about fish, but I once travelled with a guinea pig as carry-on from FRA, and all US customs wanted was a vet's note certifying good health.
Will you friend hold the fish for 6 to 8 weeks? If so just apply for one yourself. Think it is about $100 and then $95 or so inspection fee when they arrive. Assuming you have an authorized airport. If not they will need to be inspected and then shipped to you.
there was a vendor here that was from MA a while ago that originally was from RI but then either relocated or opened 2nd store in MA. Forgot the name though, Don't know whether they are still in business or just stopped being a vendor here