Compact Fourescent Bulbs are available at most Home Improvement stores. The squiggly bulbs, ya know?
You'll need to buy a few to = 5000 lumens per square foot. So, watts means next to nothing, look for the lumen rating and add that up till you get to 5k. In the same store you can double or quadruple your effeciency by picking up 3 "Y" adaptors making 4 bulbs per original socket. Get it? Plus the bulbs need to be placed very close to your plants, within a few inches. I'd shy away from specifically labeled "Grow bulbs" you'll find in the same isle, usually not worth the extra $$ in difference.
Hope this helps =)