Try this link on how to make your own.
http://www.penturners.org/forum/topic.asp?ARCHIVE=true&TOPIC_ID=11720&SearchTerms=light,box
If you make your own, make it smaller than the instructions in the link. I made mine the same size as recommended in the link and it was way to big. I've since made it smaller, but it could still be smaller, 10x10x10 is more than enough. I use a doubled white sheet to cover it.
I use 3 23watt CFL bulbs that have a color temperature of 6500K. I believe you can now get these at Home Depot or Lowe's for quite a bit less than I paid. The critical part is the color temperature, it needs to be at least 6000K, which is basically daylight.
And, be careful on eBay. Some of the people selling those things sell them cheap and then charge $15-20 for shipping. The commercially made tents are collapsible and shouldn't cost more than $8.10 in a flat rate box.