We often get inquiries regarding replacement nuts for the 108-0740-001 banana jack from Cinch Connectivity Solutions Johnson. Unfortunately we do not carry the nut separately or a viable alternative option.
The datasheet indicates that the part has a 1/4-28 thread. Keystone electronics p/n 4713 would appear to be a match.
Thanks Rick, not sure how I missed that. It is slightly wider but should work in most situations.