with a unit that old? you'll be lucky to find one anywhere.
If any of the parts on that starter are broken i doubt you will find any old new stock parts, these have been obsolete for decades. Your best bet is to look at forklift junkyards and see if they have any of those models with that engine in it that might still have an intact starter on them.
just google 'used forklift parts', there are many to choose from.
But keep in mind, this is a very old unit so it will still be very hard to find any parts like a starter for this. If you have a shop near you that repairs starters you might can take it to them and they would stand a better chance of finding anything, or they will tell you straight up if they can even fix it or find any parts for it.
This might be a longshot but i deal with a company here in charlotte nc 'American Auto and Truck Electric' that rebuilds starters and alternators and they are very good. Google them and get their phone number and call and talk to Chip, he might be able to help you.