What about the weighted "foam"? When I looked into loading the tires in the tractor that was another option. No sloshing, no rusting. But it wasn't cheap - about the same price as a tire.
My guy here locally doesn't do that - and based on what I've read that's a real nightmare if you have to repair the tire. The beet juice is messy to drain and refill - but the foam is darn near a one use deal if you have to bust the rim.