I've seen both Milorganite and ZooDoo for sale at garden shops in my town in the last couple of seasons. Our local zoo doesn't process it commercially, but occasionally has (once or twice within memory) had a "free fertilizer" day when you can go out an scoop up what you want.
I've also had the experience of buying some "discount" potting soil that, when the plastic bags were opened, looked like they just "put it in the bag" and hoped it would process on the way to market. It didn't. Still have a couple of bags I'm letting "finish."