Unfortunately there is no good answer to your question.
The fonts in the Plan 9 distribution are not the format that
the Windows sam binary expects.
If you download [url]http://plan9.bell-labs.com/sources/plan9/extra/9pm051031.zip[/url]
and extract that, then you can get a few more fonts of different sizes.
I do not know of any good way to convert Windows fonts
into fonts for sam. There are ways, but the fonts often come
out looking quite ugly.