[data to object]

You can make a selection of the objects a create a group.  The selection can be done manually by clicking on the 3D View .  Perhaps by spelling of name if that happens to be your case.

You may need to change your search to ... Python Script to [data to object] material.  Please improve my search suggestion.

A Python script can perform [data to object] for you by iterating through that group and making the change.
Currently I am not including a Script.
If someone does not provide a Script in the near future and time is of the essence, for the above you may choose to do it manually.

Multiple Materials to One Material

I saw something I believe here at BSE an question which brought up a material matching in the form of a Script.  I believe it reduces multiple matching materials into one material.
That script may be on the [Related column] on this same BSE page, 

copy linked materials nodes to local nodes.