If you can’t find a collectible needed to complete a quest, try to search at different places (benches, bins, boxes, etc.). Keep looking, you should be able to find every required item.

If you’re level 10 or above, you can get the necessary collectibles by asking for them from Cece - she is the hairdresser in Harlem. Please note though that this option is not available for wedding or audition collectibles. To buy a collectible for an audition, simply open the audition billboard, and tap on the button under the required item.