I have been looking for a Model 64 for about two months now. They are out there but most are not being sold. The everyday hunting guns seem to be more plentiful but there are some really nice collecotr grade stuff as well. Give it a try, but don't be shocked when you get substantially lower offers. The 64A doesn't seem to be as popular or carry the value of the originals. The 64A was one of the 70's guns that seems to suffer from the receiver alloy issue and resulting finish flaking.
GB #1042137132 is the gun I beleive was being referenced above. It was just relisted, again.