Yes, there are mutes you can buy for saxophones. Years ago when I studied you could only find them for alto but that's changed. I found a few here:
https://howtoplaysaxophone.org/sax-mutes

If you don't want to spend the money try putting a small rolled up towel down the bell. The problem you may have is if you put it in too far it will make it VERY difficult to play the low notes because the towel gets in the way of the those tone holes. You will be limited in your range by doing this.