Slippery elm bark source

[SlipperyTree]

Hi,
I'm looking for slippery elm bark powder that is not made from elm's in the US. I'm not sure how great elm disease is going to be in slippery elm tea, and I intend to give it to my cat, so... I have looked at many online sellers and have seen many claiming to be made in USA but none that say where the trees were sourced whether they were made in the USA or not. Does anyone know where I can find this?

 

[Raintree]

If I was considering giving my cat slippery elm bark powder. I sure wouldn't want it being from diseased American elms. DED is a big killer of felines.