Grover Peg Thumbscrew
Grover Peg ThumbscrewFrank FordGrover Peg ThumbscrewG99996452
A number of years ago I made up a batch of these little thumbscrews that are so often missing from the special spring-loaded Grover banjo pegs, I doubt they were the first tuners with locking string posts, but they about a century old.
NIckel plated like the originals, they have matching diamond knurling, so they fit right in visually.
$8.00 each (there are only a few, so no quantity discounts).