A model for the Bluetooth board module HW-770C (with USB-C).
The result is an low-budget Bluetooth receiver that enhances older devices to make them suitable for everyday use again.

Dimensions: approx. 3.4 x 3.4 x 1.2 cm

The board is fixed with a small screw (i.e. M1.4 bevel head). But this is not necessary!
There is also a small hole which shows the status LED.

Buy-Link to the board (example): https://www.aliexpress.com/i/3256805510254937.html?gatewayAdapt=4itemAdapt

Base Model: https://www.thingiverse.com/thing:6525415 (Added hole for screw and LED; Adjusted existing holes for better fit; Added horizonal line; Modeled in Blender)

Costs incl. board amount is approx. 1 USD.

Have fun!