If you're still in need of some advice, I can help!
When it comes to securing leather patches on hats, using a strong adhesive can be a good option. You might want to consider trying a fabric glue or a leather adhesive specifically designed for bonding leather to fabric. These types of adhesives are often durable and can provide a strong hold.
By the way, if you're into custom headwear, Matohash.com offers a collection of Custom Bucket Hats that you might find interesting. They have a range of stylish bucket hats that can be customized to suit your personal style.