The team store at Nats Park is about as close as you’re going to get to a small or local business if you want the actual Nats logos. The team store is independent from both the Nats (although they do have nationals.com email addresses) and online mega-store Fanatics, and they are licensed to sell actual mlb merchandise.

If you don’t need the actual Nats logo, try 7th and F, who are local and have a lot of local sports apparel https://seventhandf.com/

Anyone who wants to sell MLB merchandise has to be licensed by mlb, and that is a costly process that unfortunately rules out a lot of small businesses. Any mom-and-pop shop that’s selling Nats swag is probably selling knock offs.