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Unfortunately, we do not provide information on sourcing plants.

I would recommend checking with your local nurseries or online sources, such as Amazon, Etsy, or Ebay. They will, likely, have what you are looking for.

What I can do is offer information on how to care for the grass:

https://www.gardeningknowhow.com/ornamental/foliage/feather-reed-grass/growing-karl-foerster-grass.htm

Here is an article about the grass. It is hardy to -29 to -26 C (-20 to -15 F). Does your area get colder than that? If it is close to your winter temps, I would move them into the garage. If you have some leeway, move them to a protected part of the yard and cover them. Water them about once a month in the winter.

There are countless types of grasses, and it would be hard to identify from the photo. Many do grow to be invasive, and it looks to be an issue, here. Unfortunately, this may be a permanent problem. Aside from killing off everything in the area, the grass will, likely, persist.

You can some help with your local extension service. Taking samples to them may get you an ID, which might open up the possibility of using a selective herbicide.

https://www.gardeningknowhow.com/garden-how-to/info/what-is-extension-service.htm

It looks like last year's growth that looks dead because I see green shoots coming up. Just cut off the dead material so the new shoots can come through. Keep it watered when the soil dries.

https://www.gardeningknowhow.com/ornamental/foliage/feather-reed-grass/growing-feather-reed-grass.htm