They do make real copper leaf.
It's not that hard to learn to gild, especially using a paint mask for the size.
You would need to clear-coat to avoid a patina.
I've even had metallic copper paint turn green over time.
A good water-based copper paint is Ronan's Aqua leaf, again, using a paint mask, it's easy to "paint" a sign. I use Oracal's 810 masking.
Love....Jill