The Fender ones are Schaller compatible (originally made by Schaller, in fact). Thomann do Schaller compatibles for about a fiver (plus a tenner shipping, so get anything else you may want at the same time) - https://www.thomann.de/gb/harley_benton_security_locks_bk.htm
So just get a set of those, install them on the new bass, and you've got strap buttons that work with the current strap and if you should splash out on a new strap, you can fit the new straplocks to that and use it with either bass.