SKULabs offers a returns portal that can be configured with basic logic such as what orders/items qualify for returns and in which cases return labels can be generated. It's a self-service process until the return shows up at your door. It is not however a fully-fledged returns management product that could stand on it's own. Many still choose to use it and it greatly reduces the cost of coordinating returns with customers.
Remember, the return experience is often more important than how returns are accounted. Choose the right product for your customers. No matter what returns process or solution you use, you can create a returns bin that you process once a day/week. This is how larger retail stores process returns.