There are several stores that offer ArduPilot related products:

ArduPilot SWAG Shop         ArduPilot merchandise, SWAG. Official ArduPilot support products.
- Coffee mugs, Stickers, Shirts and so on

Buying these products, you also support ArduPilot development

Common stores Generic ArduPilot suppliers around the world. Place to get locally
ArduPilot related components and/or systems