Way back when, one of my Pixel phones came with a USB-C to headphone adapter, and another came with USB-C wired earbuds. They also used to come with 18 watt USB-C chargers…
USB-C can supports analog audio out, so your phone does all the work, and the adapter doesn’t have any smarts in it. That old adapter works on my much newer Pixels, and every phone I’ve ever tried it on. Currently that adapter is off living its best life doing exactly what you intend, but for a fusion belly dance group, instead of square dancing.
Just buy whatever cheap adapter is available at your favorite mega retailer, and then throw it in your dance bag.
If you’re one of those people who is constantly out of phone battery, then get one that can also do USB-C power-in, and you can charge your phone while it is playing music. Playing music will use barely any battery, so as long as you aren’t near empty, you should be able to play for hours.
I also have a bluetooth to aux-input adapter that looks like a USB charger (it is that, too), so it plugs directly into an outlet, and then has a 3.5mm jack and a USB-A port on it. It works fine, and I offered it to the dance group as a way to let someone control the music from their phone while dancing, but I was told that wasn’t necessary due to fear it was too complicated. It’s not, though, just pair your phone to it at home, and then next time you plug it in, it will reconnect to your phone, and be ready to go.
