Replace your old cracked PU armrests to with new memory foam Cloud Swap armrests.
I used 12mm x 2mm magnets. They are press fit for me, but used some CA glue to keep them in place permenantly.
Trim off the tabs on the perimeter used to hold on the previous armrest.
After printing the peices I used some some adhesive backed foam like this around the perimeter of the pieces and pressed them into place. They hold well and I can still remove them if needed. I would not hesitate to CA glue or even better epoxy the pieces in after making sure everything fits properly.
The author hasn't provided the model origin yet.