"If they had that in my city it would be huge!" Finding successful small businesses in other cities to replicate in your own city.

I was wondering if anyone knows a good way to approach this. I was thinking about small businesses that may be successful in another city far from where I live may be an opportunity to replicate that model in my own city. It may be a way to find a proven market with a similar demographic. It could be a shop, a B2B business, a local service, whatever.

Outside of just traveling and snooping around are there any trade publications, business journals, etc. that would be good for research? How can I tell if a business is really doing well?

Anyone know of any examples of this?