I think they may be called "pass-through buckles". They list them as that in the fourth pic of this harness. https://www.industrialsafetyproducts.com/frontline-combat-economy-series-full-body-harness-universal/
That looks like the right phrase!
It also looks like are also looking for exactly this.
Cool. I recognized them from harnesses we would use to climb masts. They're a fantastic clasp when they are comfortably taught. I don't think I'd like the offset fitting on the original one you posted. I'll see if I can dig something up.
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