I live in central jersey (Middlesex County)
I am specifically looking for perennial salvias, but in general would like to find places that stock more than the common fare found at most garden centers.
As you've found, most garden centers have a limited selection. You'll do better with mailorder, such as plant delights.
Atlock is good for unusual and not far from you.
Rare Find Nursery in Jackson
Here is a link that might be useful: Rare Find Nursery
Well-Sweep Herb Farm in Port Murray, and they also do mail order.
Great swamp in meyersville has many shade and sun perennials + many types of vines, annuals, herbs trees and shrubs
Belle Mead Bloom has a large collection of plants for sale. Not far from you. Very nice people.