Lots of ways you can do this.
Magnets. Neodymium magnets are powerful enough to hold a prop like this together. You could have one half of the prop "slip into" the other with a male peg and a female hole and have magnets glued into either piece to secure them.
Footlocker latches. It's exactly what you think.
Bolt/screw. The easiest and cheapes way is to go to the hardware store and get a heavy duty carriage bolt and enough nuts of the same size to fill the bolt up with them. Bore a hole into either connecting side of the prop. Apply Vaseline to the threaded half of the bolt and fill it with the nuts. Use a super strong adhesive (such as gorilla glue or fiberglass) to attach the bolt head and shaft of one half to one half of the prop and the nuts to the other half so that the Vaseline will keep the bolt from being permanently attached to the second half and so the bolt half will unscrew freely from the 2nd prop half.
... that was a little confusing. lemme know if I need to draw it out for you.
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