M-Edge lights are great battery are AAA I got mine at Ollies Store $3 pack of 36 batteries for $6 You can slide it between most cases but M-Edge case runs $10 at Amazon includes shipping.
http://www.amazon.com/gp/product/B00...ilpage_o01_s00
http://www.amazon.com/M-Edge-UN1-E3-...xgy_400_text_y