I downloaded and installed the Nokia 5320 XpressMusic plugin (took a bit of a chance considering it's an S60 based phone, not an S40 like the 5130). After installation I proceeded to the /Library/PhonePlugins/Nokia
5320_XpressMusic2v0.phoneplugin/Contents directory (I later renamed it "Nokia
5320..." to "Nokia
5130..." for neatness) and edited the Info.plist, MetaClassesplist, PhoneConduit.plist, and SyncEngine.plist files (the last three are contained in the Resources subfolder of Contents) replacing every instance of 5320 with 5130. Finally opened the MetaClassesplist file again and searched for "identification". Just shortly below "identification" you should find the following section:
<array>
<string>Nokia+Nokia 5130</string>
<string>Nokia+Nokia5130</string>
</array>
Replace it with (this is probably only appropriate for NAM 5130s):
<array>
<string>Nokia+Nokia 5130c-2</string>
<string>Nokia+Nokia5130c-2</string>
</array>
Save the file. Delete any Bluetooth connections you may have to the phone and re-connect. It should then appear in iSync and work correctly.
After initially syncing the phone, I was no longer able to sync it again. I would receive errors that the phone was not able to complete the sync. I deleted all phonebook entries from the 5130, reconnected the phone and everything has been working correctly since (crossing my fingers). Hope this helps.
Stephen