Page linked has patterns for newborn/preemie size, modifications for 3 month and toddler sizes, as well as amatching hat.

Measurements for newborn/preemie size:
From Shoulder at neck- to the cuff of the sleeve = 7”
From top neck down to the front = 7.5” in length.
Across back measured just under the arms = 7.5”

Also needed: one 1/2” button