Start with the obvious
Transit tickets, museum tickets, boarding-pass fragments, café receipts and attraction wristbands are easy wins because they already contain dates, places or local typography.
Look at food and packaging
Tea tags, chocolate wrappers, bakery labels, fruit stickers, takeaway seals, sugar packets and bottle labels can be more visually distinctive than a souvenir-shop postcard.
Notice local graphic design
Keep a small piece of a flyer, shopping bag, hotel card, business card, event leaflet or menu. Look for colors, typefaces, icons and language that could only belong to that place.
A 25-item scavenger list
1. Metro ticket 2. Coffee receipt 3. Food label 4. Museum ticket 5. Local logo 6. Business card 7. Snack wrapper 8. Fruit sticker 9. Flyer fragment 10. Hotel card 11. Paper wristband 12. Coaster 13. Bakery sticker 14. Transit map fragment 15. Luggage tag 16. Store receipt 17. Menu fragment 18. Event ticket 19. Packaging seal 20. Local-language phrase 21. Tiny illustration 22. Number or price 23. Pattern 24. Something unexpectedly funny 25. The one piece that tells the story.