I have been carrting mine in a pocket in my bibs in the small of my back, but I have also used the Amphipod Airflow Endurance Waist Pack. It works great to carry a phone, drivers licence, credit card, and a few other small items. I have worn it a lot for trail running and riding. It works well. I typically wear it in the front under my jersey or tee shirt.
https://www.rei.com/product/776506/a...nce-waist-pack
Edit to add that I am almost exclusively mountain bikjing these days and don't wear jerseys, but favor tech tees instead. For road riding I am more inclined to wear actual jerseys and carry the phone in a jersey pocket.