A good 2.4ghz basic radio set can be had for $20 with a FlySky GT2. It's a "nuthin fancy" set, but it works. It's what I use. Otherwise, a Spektrum radio will set you back $200. By "old Traxxas radio" do you mean the kind with the old whip antenna? If so, I'd suggest getting some sort of modern 2.4ghz set, cheap or otherwise.