Cool flourescent bulbs
 

Julie:

You can buy "daylight" flourescent bulbs from several places, I'm sure -- hardware stores, Walmart (where I buy them), etc.

The best ones I've found are made by GE. They make one that is rated at 5000 degrees Kelvin; 6,250 Kelvin and 6,500 Kelvin. These come very close to approximating north light.

For night work, I use two 5,000 degree lights, interspersed with two 6,250 degree lights.

No, it's not as good as north light, but it is as close as you can get out of a 40 watt 48-inch tube. They're not expensive, either. You can also find the same temperature tubes in art catalogs for five times the price. Go to Walmart or your favorite bulb place.