I liked the idea of loidolt's design, but I didn't have any long M3 screws. I remixed his design a bit to use a shorter M3 x 8 screw and nut.
This will require that the broken ring portion of the key fob be cut off flush. I just used a hobby knife and took small slices.
I printed mine in PLA with a 0.6mm nozzle and 0.32 layer height.
The author remixed this model.