You can find both stainless steel over center buckles and zinc-plated over center buckles at WinnerLifting.
Each over center buckle has its own special way to work with straps,to lock and to get your attension.
There are around 15 popular buckles in the market,and it's been years.Why change the good thing?Said by the people who use these buckles.
Plus,WinnerLifting is happy to provide buckle with straps,PP or PE both fine.
You can always find a practical solution for your inquiry here.