Tomioka Silk Mill

You don't need to join a tour, you can go by yourselves using the train. From Tokyo, you need to go to JR Takasaki station either by the local train or the Shinkansen, and then change trains to Joshin Electric Railway and get off at Nishi-Tomioka station. It's a quick walk from there.

Look at this hyperdia page for details about transport. http://www.hyperdia.com/en/cgi/en/search.html?dep_node=TOKYO&arv_node=NISHITOMIOKA&via_node01=&via_node02=&via_node03=&year=2017&month=06&day=22&hour=09&minute=17&search_type=0&search_way=&transtime=undefined&sort=0&max_route=5&faretype=0&ship=off&lmlimit=null&search_target=route&facility=reserved&sum_target=7