Decided to try the DoSmarter ZX28, mixed bag reviews on Amazon with some folks saying its great and very accurate while others claim its awful and very inaccurate so I guess we'll see ¯\_(ツ)_/¯

I also had trouble finding something. I ended up going with Wofit. It’s technically a fitness tracker and is pretty simple, but it worked for my budget and my issues. The app was free and it makes you a line chart of your heart rate throughout the day which i really liked (i have inappropriate sinus tachycardia). Its battery also lasts for days without charging. I hope the option you chose works well. I feel your pain on the difficulty of finding something that works. Everything is either fitness and not heath based or really expensive.