If someone comes to your business looking for a product that you do not have, help them get it from somewhere else. When I worked for FranklinCovey I actually printed maps to other stores for customers when did not have the item they needed. People were overwhelmed by the service and it was not that hard to do. But guess where those customers go first when they need something? That's right, they go back to the FranklinCovey store because they know they either have what they need or will make sure they get it.
How can you help customers find what they need, even if you don't have it?