I visited Cape Lookout last weekend and purchased a Stamp T-shirt at the Harker's Island Visitor Center. The T-shirt price tag had a web address to a site that makes military and USPS merchandice: www.ipledge.com

I visited the site and they have a whole SE Lighthouse area for anyone interested...they have T-shirts, tote bags, magnets, lapel pins and mugs:

The irony of shopping there is that their preferred shipping appears to be via UPS!