we still have "butchers" here in Australia. these are usually local shops, that sell meat. After they have cut up the large sides of beef, they are left with some bones. The bones you are after are the breast bone, which is usually discarded as waste, but is good for dogs. Get them to cut the bone (which is about 1 metre (about 1 yard) long), into the size that is good (mine are cut into chunks about 7.5cm (about 3 inches)) or whatever size you want. The cutting is done on a bandsaw so no effort on their behalf. The advantage is that there is no debris left for the motor mower to fling at your windows, or for insects to settle on. Even at the supermarkets there are some to be had, but find out from the meat section when they get deliveries. You will pay more at the supermarkets, but you should not pay more than necessary.