If you use an electric device like a tablet or smartphone, cover it with a ziplock bag to make waterproof and get ones of those dedicated pen for that electronic device and preferably a pen that doesn’t need batteries. It should be able to take notes this way. Or better yet, forget about the pen, since the device probably has a keyboard, just type it out instead of writing. I had luck watching videos in shower with the ziplock bag but I never tried writing notes in the shower.