TRS. Demon Tweeks sell them.
I evenually decided against harnesses...Why? - Pain in the ass really. The PP's buckets keep you very well supported. You need to be careful with the mounting points for harnesses. Sides are ok, you can use the oe mounting points on the car and pretentioner. Just make sure you get lap straps with an eyebolt and not a clip (I.e Sabelts) For the shoulder straps, the top of the bulkhead is the easiest bet, but through the bulkhead is neater, requires a skilled welder though and accurate drilling...
More hassle than it's worth imo....