all leather, no buckle nor velcro, just leather
Buckelelss strap , this wont scratch your new car like a stainless steel buckle will.
ideas from here and here
From a leather tag (approx 46x110mm) that came with the Polo jeans I bought years back (the other piece is not used here)

and remove the eyelet, cut the tag into 2 halves, lengthwise, and made this

String a leather lace throught holes punched on straps. Size of the holes is smaller than the lace.

lace the straps together

see, no buckle