This quest is given to you immediately as soon as you talk to Jimbo in his shop. He’ll ask you to find his wallet that he left in the strip club. Head there and find his wallet on the table to the left near the stage.
Deliver it to Jimbo to complete the quest and unlock him and Ned as a Summon that can call in battle using the Ham Radio consumable. He will also allow you to take a selfie with him.