Where to buy resistance bands

[Gams]

I know there have been threads on this before, but I guess I didn't pay too much attention because I didn't need a recommendation then. I've always bought Dyna Bands for ramping class from Fitness Wholesale. Yesterday, though, I had a very bad experience with one of their customer service reps and I decided I will tear the elastic out of my underpants and use it before I will order from them again. I normally buy the 6-foot Dyna Bands and they come in 4 different resistance levels - I only use three, though. The lightest resistance was too light for anyone really. Any recommendations on where to get something similar? I wouldn't even mind finding bands that had more resistance levels just so the students have something to move up to if they want. I like the 6-foot length, though, and the 6-inch width.