The hat worn by Gaga on the cover of 'Joanne' was a custom design by the Gladys Tamez Millinery.    Here's a feature article/interview with Gladys, offering lots of insight into her work and her celebrity clients:  http://la.racked.com/2015/10/30/9645570/gladys-tamez-studio-tour     An excerpt:  What's your bestselling hat to date? The Bianca from our Fashion Icon collection. It was inspired by Bianca Jagger in the '70s; every girl looks good in