I'm not sure such a thing actually exists...at least, I've never seen one.

All I can tell you is keep doing what you've been doing. Make note what shows match the genre you like writing for then watch a few episodes to get an idea when the commercial breaks are.

Channels will always change when the breaks are over the years and based on need. I'd say stick to the 5 break method. It's easier to convert a 5 break script into a 4 break script than it is vice versa.

Also, be aware that the future of TV seems to be streaming channels like Hulu or Netflix. The need for "commercial breaks" as we know it is dying. So I probably wouldn't spend TOO much time worrying about it.