I have done this for all of my smart watches in the past and now for the Amazefit Trex Pro.

A Wall Wart for holding the watch while charging.  

You will need:

1. US iPhone 5w Charger
2. Amazefit T Rex Pro Charger
3. 3D Printer

Installation:

1. Run the usb connector thru the slot into the inner cavity until the connector is in the slot
   1. Adjust openings as needed
2. With all the cord out the large opening, coil the cord back into the cavity
3. Plug in the USB into the iPhone 5w charger
4. Push the charger into the cavity
   1. Make sure it is a snug fit
5. Plug into a electrical socket
6. Place watch on charger
7. TADA