I found Cowlacious makes audio activated switches that seem to work perfect for my cannon, but they are out of stock.
www.cowlacious.com
Anyone know of something similar that could work as a standalone controller that's activated by audio?

Audio Activated Switch
Cowlacious Designs sells prop controllers, sound boards, and talking skulls for use in Halloween props, amusement parks, museums, miniture golf courses, and any other area you need special f/x in.
Anyone know of something similar that could work as a standalone controller that's activated by audio?