I received the Kuiu Pro G3 harness today for my BR10. The large size fits the BR10. Gunwerks suggest it. Waterproof and very lightweight. Comes with three pads that go inside on the bottom for fit. The BR10 fits perfectly with the thinnest pad. I bought the cellphone case which has two padded pockets. One for the phone and a smaller pocket for an extra battery. I took the shell carrier off the bottom and mounted the accessory pouch there for my glasses. Also has a web pouch in the back. Two small pouches on the side. Room enough for the WeatherFlow.
Marsupial has a similar product. With the Marsupial, you can mount a pistol holster on the bottom. I don’t think the marsupial is waterproof though nor can the fit be molded. Could be wrong.