comments:
You can either take your chance with off-brand batteries from sites like Amazon, or hook-up to an external power supply. The door should be removable, however, your GoPro won't be weatherproof, without the door. For external power supply, I've been quite happy with Suptig, so far. I like how it's designed to go on mounts, while mounting your GoPro on top of it. If this one is too heavy, they do have a smaller model as well. Many people say that Telesin batteries are quite good, but I have no personal experience with them.
Power banks ahould work. Even without the battery inside, which I recommend, as most power banks tends to shut off, when the battery gets fully charged, plus constantly topping up the battery is not good for it either. I got a Suptig power bank from Amazon. It's designed to go onto mounts, while mounting your GoPro on top.