Mary Ellen,

Try using https://www.jewishgen.org/Communities/Search.asp
You can do a soundex search on the town name. 
Keep in mind that most towns had several names in different languages, including Yiddish variant town names.  The above database includes these.

Where did you see the town name Sibishoff?  Do you have this person's naturalization papers, passenger manifest, or other records that may list the town of birth?

 Regards,

Sherri Bobish