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.