How do I get golden weapons? (Dying Light)

Receipts for Bozak, for example.

1.By passing Bozak's test, you can get receipts. By exchanging them with the storekeeper, you have a small chance to get golden weapons.
2. You can go through a prison in less than 8 minutes.
3. Search in police vans, but tried it myself, did not find it.
4. Search in white chests or in the VGM chests (they are in the quarantine zone).