There are some advertised in the magazines that run about $27 cone and $3 ball but I understand they are fairly light weight. Ideal Harness has the heavy duty ones for about $50 cone and ball.
Gayla Driving Center -502-863-5113 and Driving Essentials 800-622-8543. Gayla advertises at $27 a piece plus shipping and handling. Driving Essentials doesn't have a price you would have to call.