I'll be watching this thread. I have a set of gold-plated Planets from the same era that need service, and I couldn't find anyone who does the work. If you find someone, I'll probably follow you in.
That said, the two-tab Grovers pictured here were fairly common back in the day, and there are still lots of them around, owned by people who put more modern (and, honestly, better) tuners on their conversion necks. An option for you would be to find a collector or an upgrader willing to part with a set that works better than yours. The price shouldn't be too scary.
Keiths, with or without stops, will radically change the look of the banjo. Rickards, Waverlys or Gotohs would be more traditional looking. But I read the OP's previous thread about the banjo and I think his intention is to keep it as original as possible. Hence overhauling instead of replacing the original tuners.
Another problem - any modern tuner is going to leave the screw holes of the original tuner tabs visible. That won't look good even with a traditional looking tuner.
The problem is dried grease, formed into lumps, making the tuners act they way they do. Moving a solvent through the tuners to dissolve as much grease as possible will help. I've had the best luck with a syringe and plastic tubing to wash out the tuner body. Remove the tuner from the banjo, remove the tuner button from the tuner, soak the tuners in solvent for a while or hours or days, rig up your flushing apparatus, and douche away. Rotate the gears a few times while douching, er, flushing. Evacuate the solvent, let dry for several hours, and re-lubricate with an oil product that applies wet then gels into a grease. I've had good luck doing this.
I just read your earlier post. You have the TB-3 BB banjo that was re-assembled incorrectly. Your problem may simply be that the tuner button screws are overly tight. This will definitely affect how they operate. Back off the screws and see if it makes a difference. Tighten the screws about 1/2 turn after the screw makes contact with tuner button. Firm-ish, not tight, is what you want.
Thank you very much everyone! To clarify, I'm wanting to put this banjo up for sale on the Hangout for a friend. I don't want to do any renovating as prospective buyers might like it in it's most original form. -Robert
The tuners are advertised regularly for asking price around $100. I doubt they bring that, because they are terrible, even cleaned and greased. I’ve got 2 or 3 sets. You might be wasting your time, but you might enjoy the tinkering.