All other models I found made the TRMNL stick out too much or used magnets that I didn't have on hand. This one uses 6x2mm magnets (stacked twice) and has a thickness of a just a few layers. The model attaches to the TRMNL with double sided tape for additional stability. 

Print using 0.2mm layer heights. No supports needed. 

A step file without fillets or holes is included for easy customization.