Daniel: One of the reasons I order two of those sets was to get those bulbs, and extra light bulbs. Without some "good" lighting, the tents/cubes are not worth having. The best prices I have found on those bulbs were on Amazon, and they are still over $10 each! Considering I got 6 softboxes, two of the light cubes, and 6 bulbs for $120, it was a no brainer..... cobbling it all together from the cheapest sources I could find around the net would still have cost me nearly $600.
What I did was go to the local Home Depot, and purchased socket extenders, and 2 to 1 socket adapters. This allowed me to use two bulbs in each softbox.....which makes a dramatic difference. The bulbs that came with the sets I purchased are 6500K (daylight bulbs). Probably the biggest thing I've learned about knife photos is using "daylight" bulbs (5500K to 6500K which is usually written on the bulb base, or the packaging). One thing I learned that is very important is to NOT have any other light sources going when you're shooting. To explain, my photo table is setup in my basement....where all the lights are florescent..... if I have ANY of those lights on while I'm shooting knives, the camera picks up those light sources too, and the photos come out very "yellowish" because of the different light colors/temps. Most of the household bulbs, tend to be around the 2700K color spectrum, which is very yellow in color compared to the "daylight" bulbs.
Another "trick" that I use for knife photos is to get a piece of clear glass, and raise it off the bottom of the light tent/cube......then place the knife to be shot on the glass, and the background below the glass. I find that it give the photo more depth of field, and I personally like the way it casts shadows....gives a better perspective of the knife being shot. Here's a pic of a EBK with the knife sitting on glass, and the background on the bottom of the light cube:
