There are two replacement fasteners. One uses a 10/32 threaded screw, and the other uses a barrel fastener and screw. Examine the hole in your climbers to see if they are threaded or smooth.
996: Single Piece Threaded Fastener for Climbers with 10/32 Threaded Holes. (Sold in packets of 4 fasteners).
9215: Two Piece Barrel Nut Type for Climbers Without Threaded Holes. (Sold in packets of 5 sets of fasteners.)
A9215- Two Piece Barrel Smooth Type for Aluminum Climbers. (Sold in packets of 5 sets of fasteners.)