I know a *little* about aircraft restraint engineering
So the buckle shown in that photo is what's called a "rotary buckle". Are you looking for the military style with the 3" wide webbing and lever release you see in many military and vintage aircraft? Something like this?
I worked with Scott @ Hooker Harness for 20 years as one of their suppliers and would go to them without hesitation. https://www.hookerharness.com/aviationsport.html
I might have had manufacturing build 4 x four-point rotary buckle restraints with inertia reels for our -10...
Crow makes an excellent harness and their lever-style rotary kam lock buckle is really convenient. I upgraded my previous non-lever rotary kam lock to the lever style because I found that you had to grip the release knob pretty tightly in order to turn it to release all the buckles. I upgraded because it was occasionally an issue if my hands were sweating, and the worst-case-scenario EMT in me whispered that it would be even more problematic if my hands were bloody.