I've been told that any feed store or mill that handles Purina products can order mazuri. Whether they will or not, and whether the price will be acceptable, now that could be another story. I know with tractor supply, they can only get what their distribution centers stock, and that varies from DC to DC. A regular independent feed mill/store won't have that issue. My local mill keeps a few bags in stock for me, so I go in and get a bag a week or more on average. $28 a bag kind of sucks though, so I wouldn't mind finding it cheaper.
Edit: Oh, and if anyone was wondering, the sudden shipping cost increase is due to the weight causing it to have to go freight instead of regular shipping. As in they have to stick it on a pallet and ship via truck. You could probably get 40 bags at the same shipping cost, or close to it.