Where to buy small 4wire slip-ring with built-in pot or position sensor

[Psi]

Hey guys, i'm trying to find a small slip ring which provides 4 contacts as well as position information about the rotation.
Doesn't really matter how the rotation sense is done internally but i would much prefer an absolute value as opposed to being relative to start position. A continuous rotation pot would be ideal.

Size doesn't matter to much, but ideally smaller than 4cm width wise.

Anyone seen something like that for <US$30 ?
Or, failing that, does anyone have ideas for getting position from a slip ring externally which would be easy to do mechanically?
Best way i can think of is a magnet and hall sensor, time each revolution using a micro and calc the angle assuming constant speed.

 

[eurofox]

On ebay 

http://www.ebay.com/sch/i.html?_trksid=p3984.m570.l1311.R1.TR8.TRC2.A0.Xslip+ring&_nkw=slip+ring&_sacat=0&_from=R40

[Psi]

yeah, i know you can get slip-rings on ebay. I'm looking for one with a built-in continuous rotation potensiometer.