Window seal felt - how to replace?

I have a big problem with my windows. The fuzzy seal around my windows is gone, and I can't figure out how to replace it or where to buy the replacement seal to go in it. Without this felt seal, the windows rattle and air and dust flows around them when closed.
I also can't figure out how to get the sliding window to come out. Does the whole unit have to be removed from the trailer? I hope not.

I will attach a photo here. Help?


https://photos.app.goo.gl/HG6Fz2UT4xt8eMUUA