Here's an interesting idea: Fontlab, the makers of numerous Mac and Windows font design tools, is offering online "rental" of their TransType Pro program. TransType Pro is a "universal font format converter for Mac and Windows" that "allows you to convert practically any font into any other format on Mac and PC".
TransType Pro costs $179. But a 24 hour rental of TransType Pro, through a partnership with Roozz, is less than $10. If you just have an occasional need to convert a font, or you have a batch of fonts to convert and then you'll never need the software again, this might be a very cost-effective way for you to get the job done.
Unfortunately, Roozz is Windows-only at this point. They claim to be working on a Macintosh version.