I've also just mapped it to Ctrl+Alt or something as well. But ultimately for a daily driver I just got a Unicomp with the super key and use my old one with my retro rig now.
Unless you are super nitpicky practically identical other than the branding. Former Lexmark and IBM people bought the actual stuff used to make them over the years and formed Unicomp after it was shut down so they are not cheap knockoffs.
I did read that the molds used in some models were starting to wear out, but they have new ones that seem to be getting good reviews.
So yours is almost 40 years old, nice. It's amazing how far technology has moved in that time and here we are still using these ancient keyboards... they have seen some things we wouldn't believe.