It's from an obscure Chinese toy "Electrical" sword. It cost me less than 2 bucks but the wiring is completely different than the Hasbro boards. I figured it out with a little trial and error.
It's not the sort of thing I would normally put in a customer's saber, but this project called for some creativity to keep within budget and I was assured the client would love the sound. (Kids don't tend to be very picky about such things)
To give you an idea of the budgetary goal, the cost of the project was less than the cost a regular Force FX saber.