If you're able to bring yourself to a Target in the area, they usually have Harry Potter/Disney merchandise for a lot cheaper than what you would find in the airport or CityWalk. Not as "authentic" feeling but it definitely helps if you find yourself on a tight budget. Make sure it's a Target relatively close to Universal Studios - I live in Davenport (half an hour from Universal) and they don't sell US merchandise at our local Target. I know the one off 192 (15 minute drive from US) does.