I think it would help if you gave us an idea of your needs. Do you have a minimum resolution/FPS requirement? Is weight or size important?
If you're looking for a camera with the same or similar specs (size, weight, resolution, record fps) as a gopro hero5, I'm sure they are out there, but I'm not familiar with them.
If you're looking for just any actioncam, I'm a big fan of the mobius actioncam. It's smaller, doesn't record in as high a resolution or framerate, but is suitable for my needs and only cost about $60-80 when I got them. There's a newer model, the mobius2 that's closer to the $80 range out now, but I have no experience with it.
Runcams are also popular and of a similar form factor as the mobius, but I have no experience with them.