More information and detailed startup guides available at: https://tinkerbugrobotics.com/
Source code and PCB files available at: https://github.com/Tinkerbug-Robotics/TinkerNav
Open source hardware and software project that delivers 1 cm location accuracy for your next project
They are hard to find, but the store is https://navspark.mybigcommerce.com/
Shipping is high if you are only buying a few unfortunately.