Nokia doesn’t provide a C3-01 iSync plugin. I found a post for a C3-00 plugin and there in the comments was a link to a C3-01 plugin.

My only complaint is the phone icon that appears in iSync has a white background and the image of the phone is small. I found a high resolution image and created a new image for the plugin which is available for download.

When you get it replace the image ~/Library/PhonePlugins/Isync Plugin C301.phoneplugin/Contents/Resources/ with my version.