These work well with the Retroflag cases:
https://www.amazon.com/Yuconn-Charger-Adapter-Raspberry-SoundLink/dp/B071YC2T9S/ref=sr_1_8?crid=34BLHM7O17UD&keywords=raspberry+power+supply&qid=1558364299&s=gateway&sprefix=raspberry+pi+ower+s%2Caps%2C145&sr=8-8