either ge or phillips makes a "natural daylight" cfl bulb (spiral) in 6500k. you can get them pretty cheap at walmart, home depot, ect. if you cannot fit a cfl, i know petsmart sells elongated cfl's for strip lights in 6700k. you could probably find them pretty cheap online as well. another option is led lighting. i forget who has them, but one of the sponsors on here sells led lights that screw into an incandescent socket. pretty pricey compared to a cfl, but saves money in the long run because led's last so long.