My SJCAM M10 Cube Mini Full HD Action Sport Camera (US$69.95, no tax or duty in Canada) just showed up in my mailbox. I had ordered it from Ali Express about six weeks ago. The kit includes a spare battery, charger, waterproof case and a pile of GoPro-compatible mounts. Shipping was free but, as it was presumably surface mail -- direct from Shenzhen, China -- it took a while to get here.
The camera is a 1080p GoPro clone with a more cube-shaped form factor and is well reviewed. In any event I wasn't about to spend $300-$500 on a toy so it will have to do.
I'll let you know how it works out.