As far as getting teawares, maybe plan a side trip from Tokyo to Mashiko. I can give you pretty detailed directions to get there that are probably pretty easy to follow and also info on a couple of places to stay in town.
One simple route is to take the JR Shinkansen from Tokyo Eki (station) to Utsunomiya and then the Toyo bus from just outside Utsunomiya Eki (station) to Mashiko. It'll take about 2 hours, one way. The other route is all via trains, but there are a few train changes and at one point the train you will be on splits... with the front cars going whre you want to go and the back cars not
....and no English announcements happening.
Here's a great English language train travel planning tool for Japan: http://www.hyperdia.com/en/
With hundreds and hundreds of active potters working in that one town (probably the largest single geographic concentration in Japan at the moment), and working in diverse styles/techniques, you can't HELP but find some teawares that would "float your boat". At all pricepoints from "mortgageable" to amazingly and absurdly inexpensive for the quality.
Make sure to check out whomever is showing at Kanoya Gallery (on the Mashiko Sankokan end of town), and also the work in the two Yamani gallieries (near the "Potters Square" with the giant tanuki).
If this interests you... let me know. Also see the "show off your teawares" thread for some Mashiko info I just posted there.