There’s a table tennis shop on the corner of Roosevelt Rd and Keelung. You can ask there. There’s a table tennis club that meets on Saturday’s at No. 77 Dunhua S. Rd, Sec 2 (Zhong Ding building), two blocks up from Far Eastern Hotel. I heard those guys are really really good. This place is easily reached on many bus lines and close to Carnegie’s and Taipei Sports Bar.