It is not an authentic type of Onsen, but "Oedo Onsen Monogatari" (http://daiba.ooedoonsen.jp/en/) is a good one to visit. You can try so many kinds of Onsen at once and the price is quite reasonable too.
If you would like a traditional type of Onsen, then to "Saya-no-yudokoro" (https://www.sayanoyudokoro.co.jp/english). From their exterior, you can forget that you are in Tokyo. The water is bit green and that makes you really feel that you are in Onsen!