I have the one from Performance.

If you're a skinny butt you might consider the Aspide Glamour FX.

There is also a tri version the AG TriathGel. A friend ordered one for her Cervelo P2C but I haven't seen it yet and don't think she's used it for a longish ride yet. But I'm anxious to hear how she likes it because I'm thinking of getting one for when I do tris.