Something similar to the FedEx package Return Program

We need an easy way to create non-order-related returns. We travel and exhibit at various conferences and often ship products to the venue. We need an easy way to take along pre-printed labels to send back whatever product we don't sell. That being said, we will have no way of knowing the exact dimensions or weight of these packages. We're familiar with the FedEx package return program and this is the exact kind of feature we would like to see within ship station, but we would prefer to use the associated UPS account.