Just a couple opinions based upon my experience.
Regarding warranty support on an unknown origin Kowa:
I own a second hand TN2 that I was given by an old family friend before he passed. It’s probably 40 years old by now at least. It’s a damn good scope and stands up to those made today. I contacted warranty support just looking for who I could send it to to get a once over and cleaning. For $80, including shipping, I sent it to California and received it back in two weeks all cleaned and with a good bill of health. Yes, this was about ten years ago, so that’s my perspective.
Both vendors mentioned above, Scott at Liberty Optics and gratefuldoug of Cameraland are solid and should be considered for optics if they carry what you’re looking for.