The following mikvahs are available in Manhattan:

The West Side Mikvah
236 West 74th Street
(between Broadway & West End Avenue)
Mikvah Tel. #: 212-579-2011
www.WestSideMikvah.org

Jacques And Hanna Schwalbe Mikvah
419 E 77th Street (Between 1st & York)
Supervision: Rabbi Krasnianski
http://www.chabaduppereastside.com
Chabad of the Upper East Side
Mikvah Tel. #: 212-359-2020

The Rennert Mikvah of Fifth Avenue Synagogue. 
5 East 62nd Street
Contact: Esther Abrahamson
http://fifthavenuemikvah.com/
http://mikvahnyc.com/

Shul/Org. Affiliation: Fifth Avenue Synogague
Mikvah Tel. #: 212-753-6058

Information courtesy ofmikvah.org