I wouldn't go with stiff leather, if you bend over everything might spill, make sure pockets are deep.
My favorite to use is a quick release "fanny" pack, it has a net to the side and a open pocket for junk, and one deep zippered pocket for something I might want to keep.
I do recommend the quick release adjustable belt though, that will also hold your digging tool esp, if you are returning to car frozen, tired or over heated or being followed by creepy people, you can quickly snap it off and set in trunk and sort things when you get home