NRS Cam Buckle Bumpers
These buckle bumpers are solid! The seem well-made, fit the Green Chile buckles perfectly and without any loose play, and should do a good job protecting the more delicate surfaces. They're a bit pricey for what they are, but ultimately worth the extra, I think.
I use it with my watertight bags
They're a great idea, and no down side as they fit perfect and seem to do a good job of keeping the metal of the buckle away from anything under them.