I haven't found a local that sells filters yet. Not that I've tried. This past week after running out of unused filters I used the same one a few times a day. It doesn't tear when rinsed under water or drying. The coffee filters through just like with an unused filter.
So if you're in a pinch just reuse the last one.
I believe there are also cloth filters you can buy from them as well! Last through multiple washes and can be frozen to preserve them if you don't use them every day!