For waterproof, these are the ones I use. And the manufacturer stands firmly behind their product. Several years ago, I bought 4 or 5 of these that were apparently from a bad run. I contacted the mfr and they acknowledged that there had been a problem with one manufacturing run of this size and they replaced them ALL, no questions asked, no receipt required.
http://www.hydrofarm.com/pb_de...
If you shop around, you can generally beat the suggested retail on these.
Once, when I ran out of space on my heat mats, I put clip on lights with 60 watt bulbs on a shelf below the flats, with the reflectors pointed up. Had to be REALLY careful watering, but it worked pretty well. Heh, heh, I really don't recommend the practice, tho.