If you provide more context or details about "monkey business" and what kind of safe code you're looking for, I could try to offer a more specific and helpful response.
No universal “monkey business safe code top” exists in public databases. Most likely it’s a where “top” means either the top digit of the combination or a physical location to find the code.
: You must ask the shopkeeper for credit. When he goes to open the safe, watch his movements closely to learn the combination.
Without these items, you cannot complete the "Monkey Business" chapter. Hence, finding the correct is a mandatory step, not an optional side quest.