I also have a GoPro Hero 2 and it struggles in low light. Aside from timelapse, do you use your GoPro for anything else? If you just doing timelapse I’d say your best bet is to actually buy an old iPhone or Android phone and download a time-lapse app. I use an old iPhone 5s for many things; Lightning photography, timelapse, B-Roll video camera. The batteries last incredibly long given the phone/cameras size and you can process and upload the footage directly from the device :)