This guy has reasonable cost Flipper Zero Accessories, he has not only the nRF24 and ESP32 premade boards but you can also get PCBs to build your own.
Awok Dynamics Flipper Zero Accessories
Resource: http://awokdynamics.com/
RedFox’s FZ Device Site
This is not the official FlipperZero Device Page. Please click on the button to be taken to their website.
This guy has reasonable cost Flipper Zero Accessories, he has not only the nRF24 and ESP32 premade boards but you can also get PCBs to build your own.