According to this thread the Planet Waves 1/4" Female Stereo 1/8" (3.5mm) Male Mono adapter works with the Equinox for adapting most standard 1/4” detector headphones. The connection will not be waterproof. I found them on this website for $4.95 with free shipping. I have not tried these personally and have not ordered from this vendor myself so take it for what it’s worth.