I purchased a Schroth Pofii II Formula style 6-point and a set of ASM from MSAR in the UK because they were "Caterham specific".
http://www.msar.co.uk/motorsports/Race-Harnesses/Racing-6pt-Belts/Car-Specific/Schroth-Caterham-Profi-II-6F-Formula-Style_226.html
It was not a wise move on my part. The shoulder strap fittings were not sewn in, which I suppose is ok for racing but not what I wanted for the street.
I ended up contacting HMS Motorsport to see if the fittings could be corrected, and worked with Derek Mulson. He, and HMS Motorsport, were fantastic. The changed the fittings, and made other adjustments/corrections.
http://www.hmsmotorsport.com/
Basically, I think they can customize any of the harnesses to whatever specs you want. So, if you know how long you want/need the shoulder and lap straps to be, I think they could create a custom set for you, and I don't think they charge extra for it.
Definitely worth a call.
Steve