I used a clear plastic pouch with a cross body strap. It's designed to be a waterproof pouch for a large phone, so it fit my iPhone and headphones nicely. It kept my phone easily accessible for taking photos or playing music. It's similar to the one in the link below, but I got it at Dick's...
This site is run by Ivar at in Santiago de Compostela.
This site participates in the Amazon Affiliate program, designed to provide a means for Ivar to earn fees by linking to Amazon