Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:3315698.
UPDATE. DO NOT USE. The user tested out this clip and the S31 board is too loose to have stable connections on the pins. Without an S31 device to use to model, I cannot correct this. See comment section ......... Sorry.
A user requested a 6 pin version because the Sonoff S31 outlet has 6 pins on the serial port connector ( VCC, 2 pairs of RX/TX and then GND). My standard sonoff basic clip only has 5 pins.
Print it, put in pogo-pins in , connect to your USB UART TTL adapter and it will hold the pins to the right connectors.
The pogo pins I am using are P75-E2 Convex Tip Metal Spring Test Probe Pin, 1.5 mm Diameter. Link here https://www.amazon.com/gp/product/B018YPQ6ZK/
Note: Rotate model so it sits flat in your slicer for printing.
Note2: I have not made this myself, as I do not have a S31 outlet.