This is based on the standard Bat Familiar from DND 5e. The standard stat block would be the same for the familiar itself, below are the quick construction guide for the bat.
Species attributes:
- Speed: 10 ft., fly 30 ft.
- Internal Compass: You have an innate connection to the land, so you always know where north is.
- Echolocation: Blindsight 60 ft.
- First Level Diverse Features: Hunter, Natural Weapon (claw)
- Recommended Diverse Features for 5th and 10th level: Canopy Cover, Killer Claw, Frightening Roar, Hover, Extend Special Vision, Sensitive Strike, Vice-Grip.