This is defined in template "editor_jsoptions_font" but when you search for it in AdminCP -> search in templates you wont find it?
So, the only way seems to be to edit it in the database, in table "template". Where title = editor_jsoptions_font. The fonts are defined in fields "template" and "template_un" . Just put your font on a new row.
The contents in the standard installation for fields "template"and "template_un" are:
Code:
$final_rendered = 'Arial
Arial Black
Arial Narrow
Book Antiqua
Century Gothic
Comic Sans MS
Courier New
Fixedsys
Franklin Gothic Medium
Garamond
Georgia
Impact
Lucida Console
Lucida Sans Unicode
Microsoft Sans Serif
Palatino Linotype
System
Tahoma
Times New Roman
Trebuchet MS
Verdana ';
and
Code:
Arial
Arial Black
Arial Narrow
Book Antiqua
Century Gothic
Comic Sans MS
Courier New
Fixedsys
Franklin Gothic Medium
Garamond
Georgia
Impact
Lucida Console
Lucida Sans Unicode
Microsoft Sans Serif
Palatino Linotype
System
Tahoma
Times New Roman
Trebuchet MS
Verdana