We have some growing in the yard, or rather on some bricks in a shaded, moist area. I could send you some, but not sure how well it would transport. If we are talking about the same kind of moss. Let me know. I‘m in Shreveport.
Maybe find a wooded area where there is some moisture....and look around.
Note, I have never made hypertufa, but there is always a recipe for adding moss to the mixture — it always includes something like buttermilk.....so maybe, an area with acidic soil (or acid-loving plants).
Not sure if the moss in the 3rd picture is still viable as it’s been exposed to sun.