Well, I'm definitely not the chief authority on this (quite the contrary, actually) but I was trying to scope this out.
In many of the pictures I've seen depicting GAoP sailors, belts are more of just...sashes, for lack of a better word. From what I can tell, quite a few pictures depict mariners with (what I assume to be) cloth tied around their waste.
I've also seen pictures that lead me to believe that leather (I think) belts with buckles weren't uncommon.
As for the ring belts, I don't doubt that it was possible -- just how common it was.
Alas, as I finish my post, I realize I was little to no help. Oh well. I bet Greg or Foxe would have a better grasp on the subject.