I actually did a lot of research on this and as far as quality goes I don't think you'll beat this.

http://www.cronusdevice.com/cronus-device.html

Here is a really cheap one, people leaving feedback say that it does support xbox to ps3 though it doesn't explicitly state it. I'm not sure about the latency on it though.

http://www.amazon.com/Playstation-Xbox360-Controller-Adapter-Xbox-360/dp/B0042SB2I0