you can buy keychain rings off amazon which fit into holes on the switches. i used tweezers to bend down the pins so they dont poke. and thats basically it! the original idea isnt mine, btw. thanks for the interest!! :))
It wouldn't be that difficult to put on a new chain. A pair of needle nose pliers and something like these: https://smile.amazon.com/gp/product/B07DC9YZXV/ (I've got a ton of them if you want me to mail you one so you don't have to buy a pack of 100)
Hey, OP! If you have the time, some money for materials, and need an idea, you could make some mini mushroom keychains! It's a 2 inch pattern, and they work up quickly. They're something I use for craft fairs, and people love them. I use this pattern here: https://www.amigurumitogo.com/2020/01/crochet-mushroom-pattern-2-inch.html
You could also get some of these to attach to the top of the mushroom: https://www.amazon.com/KINGFO-100PCS-Nickel-Plated-Connector/dp/B07DC9YZXV
They're keychains with jump rings, which you can open and close to your convenience. By having it open, you can slip the last ring at the bottom (the smaller one) through the yarn at the top of the mushroom, close it up, and you're done!
I hope this might be a nice idea for you; the mushrooms don't take long to make at all, I promise! You could even make them into pairs of earrings, too!