INGO swag isn't available on a continuous basis. Lots of people have brought up that they would like to purchase hats, stickers, patches, shirts, etc from an online store and Fenway has talked about it, but it hasn't materialized yet. Hopefully, with the new server project out of the way, he can put some more serious time into it.
Instead, INGO periodically offers new items online and you can jump in on those one-time purchases. The only other option at this point is to go to the Indy 1500 gun show where they show up and offer items for sale.