Which one are you missing? I managed to collect them all before they were discontinued, albeit by a bit of cheating as I had not visited Gifu but was able to find the mug at KIX. I know a few friends have partial sets and maybe they have the one if are missing.

I got three from the Tsugaru series in Feb 2020 but was missing the Goshogawara one as it was out of stock. I remember the staff said that they don’t have a restocking schedule, and only receive a dozen or so every time.