The absolute best fabric for me and my allodynia (PN) on my back is old silk. I have 2 old, very good quality silk camisoles that I can't live without. I did just buy some tank tops that I use as camis. They are from LL Bean and are 95% cotton and 5% spandex. They are okay if I'm having a good day, but not so great if the pain is bad. Still, better than just about any other fabric.
I am not familiar with elastane.
Maybe you could find some old silk camis or slips at a vintage clothing store, but it seems like it would be quite an effortful search. Really good new silk items are gonna be really spendy. You might find something in polyester or cotton/poly blends. I object to polyester because it is a plastic, and environmentally unsound, but sometimes you gotta do what you gotta do.
I hope this helps. Best wishes to you.