Knee brace/pad recommendation?

[Stabber]

I'm looking for something that will absorb impact on a gym mat, as well as support my knee during twists etc. During martial arts class, I sometimes have to come down on my right knee. Hurts like hell.

It has been sore for a while due to the twisting and impact with the gym mat.

Can anyone recommend a brand/type of knee pad or brace. And if possible, where I can find it? (ie: rite aid, walmart)
Thanks

[VDubb]

I've had excellent results with the bands that wrap around just below the knee. I have tendinitis, but I imagine they would help in this situation.