If you have a supernatural entity who can supernaturally change forms--- are you confined to making him a genuine real-life species? Because if someone takes the trouble to specify a scientific species, I'm going to expect the rest of his profile to complement the characteristics of the species are. So for someone who turns into a vampire bat--- vampire bats have a range over large portions of Central and South America, so I would associate that more with guy named Don Alfonso de Lupita y Luna, whose ancestral home is amidst the jungles of the Yucatan or who comes from an ancient Amazonian plantation, rather than someone who's from Eastern Europe or is thoroughly American and is lacking those explicit cultural roots.
But at the same time, having a thoroughly American vampire--- if he turns into an Eastern small-footed myotis, that's a bit more oddly specific that it starts being clunky, in the effort to superimpose a make-believe supernatural species with a real-life scientific species.
If you do want a real-life bat, the bumblee bat (aka Kitti's hog-nosed bat) is slightly smaller than a canary, is 1.1-1.3 inches long and has a wingspan of 6-7 inches. It lives in Thailand, etc.
Canyon bats live in Oklahoma, among other places, and are 2.5-3.5 inches long, with a 7-9 inch wingspan.
Eastern small-footed bats and Western small-footed bats are also North American, are 3-3.5 inches long, and have an 8-10 inch wingspan.
Tricolored bats are 3-3.5 inches long, with an 8-10 inch wingspan.
Yuma bats are 3-3.5 inches long, with a 9-10 inch wingspan.
Indiana bats are 3-4 inches long, with a 9-11 inch wingspan.
A little brown myotis is 2.5-4 inches long, with a 9-11 inch wingspan.
But if you were to use a real-life species, it would be cool to work in characteristics pertinent to the species into the characteristics of your character, rather than only having it be relevant due to size.