Fonts do not reside in Rhino, they reside in your Fonts folder. Rhino can use any OpenType or TrueType font it finds in that folder.
In order to do what you want, you need to install a single line text font and use _TextObject and not _Text. There are a few single line text fonts out there for downloading, here is one link…
Well, if those are fonts, they have a certain line thickness, so they are most likely outline fonts, not single-stroke. So I’m not sure you can get what you want very easily.