Reply to Controller build - problem with x-fader

Hello,
I'm currently building a fairly basic controller for traktor, based on the u-hid chip. I'm having some problems trying to get a x-fader to work well though.

I have tried a standard cheap linear pot that had a horrible feel to it and didn't seem to be linear at all (perhaps the shop gave me the wrong part).

Also tried ripping the x-fader out of my 2channel numark mixer which works, but only across the middle section of the track (where the carbon is thinner).

Basically I'm after a high quality linear sliding pot, can anybody suggest one?
I wondered if a x-fader from a more expensive mixer (with adjustable curve) would be linear?

would be grateful for any help.
Ben