I find lots of bones along the train tracks! it's usually opossum I think. That seems like the approximate size you're looking for?
Sometimes they're smashed, but usually lots of the bones are in okay shape. I'd wait until the animal is totally decayed and the bones have started bleaching in the sun or whatever. I get grossed out by fleshy stuff so I try to look for ones that don't have ANY sort of rotting material on them, but that's pretty hard to come by.
Collect and boil, then soak in bleach! At least that's what I do. I think you can use dish soap too.
I make lots of jewlery and things and put them in my dreads
I usually just use the vertebrae though, they already have holes in them!
I'm actually vegan but to me it doesn't seem so wrong to adorn oneself with the remains of animal if you find it you know? Lots of people tend to disagree haha.