I ordered 8 of them from www.bghydro.com (bettergrowhydro) and got them for $7.60 apiece.
They ship quickly, securely, trackable and have a good return policy. I've ordered 4 times from them and have had only one problem. One of the T5 bulbs didn't work. I e-mailed them and they shipped out a replacement within a couple of days with a return label and postage paid.
I'll order from them as long as their service stays good and their prices are pretty decent.