I have a couple of the countycomm delrin holders for 18650. I can vouch for both the quality and the cost. While pricey I haven't found/seen anything I like better. (3D print may be an option if you have a resource you can use)

I tried the Mac app on M1 Mac mini and the app crashed. I think it’s telling before the crash the apps prompt for changing airplay permissions uses the old system “preferences” instead of the new “settings” label…. Additionally, last iOS update to the companion app was 3 years ago….I think this might actually be abondonware too.