Go to your local Radio Shack and tell them you want them to place an RSU (Radio Shack Unlimited) part order.
You want to order a belt clip for the PRO-97, it's Radio Shack RSU part number 12418273. Cost is $3.49 each plus shipping.
They have their own store log-on and should be able to do this for you. There used to be a toll free number you could call to do this yourself, but they have apparently discontinued that in favor of in-store ordering by the store employees.