Where can I find affordable vintage teapots and tea cups in Shinjuku?

Currently staying in Shinjuku, Tokyo. I’m on a tight budget but would love to find something vintage or antique; a teapot and a few tea cups.

Do you know any shops or hidden gems where I could find something like that?

Any recommendations are welcome. Thanks in advance!​​​​​​​​​​​​​​​​