I can't be certain without photos, but old inside latches for Forever storm doors have been replaced with our 40-150 or 40-145 in the past. Compare both with your old hardware and see if one of these are what you need.
A quick learner from MA says:
May 26, 2021
need inside door handle for EMCO5050346 storm door. This looks like it might work, but can you confirm by looking at the picture below, please.
Bob from SWISCO responded:
May 27, 2021
I believe the 40-150 can replace this inside latch, but look over the dimensions and specifications to confirm.