Are you looking for one that stays in the tank full time? Or something more like a Go Pro?
I've spent days searching for underwater cameras to go in my basement pond, at this point I think the Icecap camera is probably the best option. I have found a webcam style waterproof camera, however it needs to be constantly plugged into a computer to view it, I wasn't crazy about that idea.
Past those two all I was able to find was very high end stuff for public aquariums. One company I contacted had a model they recommended to me, their newest, smallest and cheapest camera, starting at only $2500 lol. It looked very high quality but I can do a lot of stuff for $2500.
I know there isn't much out for the Icecap yet, but if you are ok with only viewing the feed on your phone/tablet I think it has potential. From what I've seen the image quality is decent.