I'll be printing 4x5 at the moment. I know the sun is unreliable as a light source, but I'm a little strapped for cash at the moment. I'm also planning to make some enlarged negatives from my 120 film, but even then it wouldn't be larger than 8x10.
I've been looking for a light source and I've learned a lot in the past week or two while reading on everything. For something as small as 4x5, one of those face tanning things would do the trick also, but your Home Depot suggestion sounds just as good if not better.