I'm still editing the list. Don't expect anything cheap.
Sub-18lbs is difficult without going with the standard RPF1 in an 18x8.0 +35 (which I believe is right at 18lbs).
The question comes down to needs, budget and whether or not you can afford to potentially damage a hard-to-get, lightweight, forged, expensive wheel on the street. If it's for track-only use then a 17x9 RPF1 is a much better investment.