Are you looking for a ceremonial document or citation?  There are various options available:

Mayor's Office

Request a Ceremonial Document from the Mayor
Request a Greeting Letter
Request Meeting with the Mayor

City Council

Request a Ceremonial Document from the Council President
Request the Council President for an Event
Request the Council President for a Meeting

Comptroller's Office

Bereavement Resolution Request
Citation Request Form

This is not an exhaustive list, it's the most commonly used forms.  If you are looking for something that is not available above, please contact the agency in question.