Another nomination for Jack Hooker. Quality work, and will customise to your requirements.
Friend George got a set with 3" military lapbelts and shoulder harness for his recently redone Supercub, and they're the best I've ever flown with.
For you spamcanners, Jack's Cessna kits are the solidest mounting you'll find, in my opinion; and the Factory mounting is way flimsy in comparison. The carrythrough structure fails before the shoulder harness. I've got a set in the spamcan without the inertia reel (wish't I'd have gotten that, too, have to slack off to reach the flap handle).
Just my opinion, but I've flown with lots of systems, and Hooker is great.
Thanks. Cubscout