Are you simply trying to set the text for your combo box selections? Item1, Item 2, etc (1)?
If so, you can add them on the right details tab under content by adding additional elements (2). I also set the “Selected Option” as the first element name so it is visible and not blank.
You can size a combo box size the same way as the others by embedding it within a scale box (3). You can then bind to the selected text the user selects by binding the onSelectionChanged Event on the right. If this is all about changing the actual font than never mind…heh.
Apologies if I am totally missing the point, just trying to help out. 
