This is based on the standard hawk 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.
- Bird’s Eye View: You have proficiency in the Perception skill.
- Variant - Flightless: Your wings don’t help much for flying. You have a 30 ft. base speed and no flying speed. Additionally, you can use your reaction to cast featherfall on yourself, but no other creatures, at-will.
- First Level Diverse Features: Hunter, Natural Weapon (bite)
- Recommended Diverse Features for 5th and 10th level: Natural Weapon, echolocation, Canopy Cover, Killer Claw, Frightening Roar, Hard Biter, Hover, Darkvision, Sensitive Strike, Vice-Grip