Norm has made a generous offer here. If you can’t find the parts as Tyler suggests it will be the sort of thing that will need a work around.
Most of the parts for this type of equipment are long obsolete
If it was me I’d work out a way of using the modern flap disks as they are readily available.
The bosses that hold these in place are cheap as the trades that use them often need replacements.
Then you’re going to need a bolt of the correct diameter to hold the boss assembly in place.
I’m not familiar with the threads on these but if you go to a good bolt shop and take your angle grinder in they should be able to match it.
If it’s a common thread then you may even be able to get a stud so that you can use it exactly as the more modern angle grinders are used.
If you know someone with a lathe, the skill and the spare time it would be straight forward to make the parts, however, those skills are becoming more uncommon.
