A missing parcel, an unattended room or a stockroom door can create a legitimate reason to consider a small camera. Searching for a spy cam store will reveal devices built into clocks, chargers and other everyday objects, but concealment should not be the starting point.
First define what needs to be observed, for how long, and who might appear in the recording.
A visible camera may be sufficient for a hallway or delivery area and can avoid the privacy concerns associated with recording people without their knowledge. The device should serve a specific purpose, not simply offer the smallest casing.