The width you need depends on how wide your sit bones are and how upright you sit. A Specialized dealer will have a pressure sensing gizmo for you to sit on that will calculate the width you need, but they won't have a $20 saddle. Performance Bike, on the other hand, will probably let you keep exchanging saddles until you're happy. I've got a Forte Classic that I picked up on sale for about $20 years ago. That works for me, but it's only about 143mm wide.