I was at a farmers market. A fellow had stevia plants, or their leaves, for sale. He gave me a sample of leaves to chew. They were really sweet, the real deal. I imagine if you harvest the leaves, soak them in a small amount of hot water, you’ll have a stevia simple syrup to use.
I watched several videos on you tube. Compress a lot of the stevia leaves into a jar, cover with Everclear or similar strong alcohol spirits, and let sit for 3-4 days. Then pour out the juice, mash the leaves in a sieve to get all the liquid, and cook the liquid on a pan to burn off most the alcohol. Then you have a syrup that can last for a long time.