Raw Iron... you can find it on old harness leather, and salvage them.
They will be rusty , Horse sweat and elements, but I've found them,
I've had several, lost a loop of buckles to my barn fire a few years back.
You can get the Chrome plated and have NAPA sand blast ... but the problem is, a $2 buckle become $20 buckle with labor & paint
Find an old barn and ask , there should be old dried/rotted harness hanging ....old barns are a gold mine