Figuring out a way to convert .fnt associated PNG files into TTF (or similar) is on my list. TTF versions of the system/bundled fonts would be very useful.
One of the tools in this other thread (which mostly talks about converting the other way, to PNG) will be able to do it:
Bits'N'Picas app would be my first try.
I'll be sure to post here if I get some good results!