Haha I'm not sure why you would want Speakon on your instrument, and I don't have the technical knowledge to give you a reason.
If the locking aspect is what you are after, Neutrik makes a 1/4" jack that you would be able to put on your instrument.
If the locking aspect is what you are after, Neutrik makes a 1/4" jack that you would be able to put on your instrument.