Mini Panel Mount USB Trackball with Three Buttons : ID 5063 : $49.95 : Adafruit Industries, Unique & fun DIY electronics and kits
Setup USB Trackball in RetroPie on Your Raspberry Pi - YouTube
New Arrival Usb Arcade Game Trackball Mouse Illuminated Led Round 4.5cm Ball Usb Connector With Screws For Mame Raspberry Pi Pc - Coin Operated Games - AliExpress
Arcade Trackball USB PC / Raspberry Pi - Arcade Express S.L.