You should find those lights in the lighting section of said stores. I don't think there is such athing as a 20" light. You may have to replace the lights with 6700-10000K lights if they aren't in that range already. The ones I've seen are 4200K.
Yeah, they are called Compact Flourescent lights, the white spiraly ones. You can get either a 6 pack of them for 10 dollars or 2 of the ones I mentioned earlier for about 12 dollars.