[gutvol-d] Need help finding a "free" font for Greek letters

The new version of the PGTEI conversion process is able to "embed" a TrueType Font into the PDF file to handle characters that are not in the default PDF character set. I'm currently working on a math text that makes use the Greek alpha, beta, gamma, etc letters. Greek isn't included in the default PDF generator. However, if someone can find a "good" TTF for those greek letters, Marcello tells me we can add it to the system. I freely admit that I don't know enough about Greek or fonts to tell what font might be good. A google search turned up quite a few that claimed no copyright or licensing encumbrance, but I need some more expert advice. So, you Greek experts out there, what font file do you recommend we use? Josh