i’m now a bit sceptical about attaching electronic devices like cameras and phones in pouches to the bike. Had an old digital camera i used to take out in a lowepro pouch attahced to the stem for convenience of taking pics quickly, unfortunately it just stopped working. Could just have been it’s time was up but the constant vibrations may have added to that, I don’t know. Now i either stick the replacement in in a pocket or take a bit more time and get it out my bag.
aquapac and ortleib cases are pretty good, see what fits your phone and how you want to carry it. Can also get some waterproof armband holders