I know that there are a couple people who run 4-point harnesses, but they hook into the back seat rather than a harness bar. A good option for a dual duty car, though obviously the bar would help in terms of long term comfort at the track.
Make sure you get a "real" harness bar. The one for the MY04+ can fit our vehicles due to the swiveling ends.
Sparco makes nice ones. NRG Innovations' are not hade with the right materials and have no internal reinforcements. thought you should know. They are alot cheaper but they are for show factor and not safe. They collapse quite readily.