I created this pattern and crocheted these baby sneakers for a friend. They should fit most newborn baby feet. You can sew the sides of the toe to each side of the sneaker if you choose to do so. This will help to keep any baby toes from wiggling out in between the side of the sneaker and the toe piece.
Free Pattern: https://thecrafterlife.com/baby-sneakers-crochet-pattern/