Another thing to inspect is the tie rods. When they get worn the steering linkage can vibrate in relation to the knuckle. You can check this by raising the entire front end up off the wheels and wiggling the tires in/out at the top/bottom and then at the front/rear of the tire. The tires should not wiggle. If they do you'll need to replace the tie rods that are loose in their sockets.
There is a newer type of wheel balancer that you may want to try and find. I believe Hunter is one of the manufacturers. The machine has a roller on it so your tire is loaded and it spins on the machine. Supposedly it can locate the stiffest part of your tire sidewall and can find where on your wheel it is (for lack of a better word) flat. It matches your stiffest sidewall point of the tire with the "bad" spot on your rim to round out your wheel/tire combo the best.