I don't know of any camera shops in Narita but 10 hours is enough for you to go to Tokyo, do some shopping, have a meal and go back to the airport.
You can take the Narita Express train (NEX) to Shinjuku. Just next to the Shinjuku station are the Yodobashi and Bic Camera stores. More info on the NEX (tickets, timetable, etc) can be found here:
http://www.jreast.co.jp/e/nex/
Exit from the West Exit of Shinjuku station (both stores are there and are quite near each other). Refer to links below for map and more info of the stores. This Yodobashi outlet is the main store of the chain.
http://www.japaneselifestyle.com.au/tokyo/shinjuku_map.htm
http://www.japan-guide.com/e/e3011.html
Be sure to give yourself enough time to navigate your way through the Shinjuku station. It can be quite a maze if you've never been to such a station before (not to mention huge as well). If you like, you can get a map of the station at the information counter.
Also, buy your return ticket beforehand to ensure that you can get back to the airport in time. I think you should be able to buy it at the airport. If not, buy it when you get to Shinjuku.