Yo Tim!
I'm assuming the cable supplied by Infiniti is the original Apple connector. You can do one of two things:
1) purchase a converter from Apple
http://store.apple.com/us/product/MD823 ... r?fnode=72
- This is the 30-pin to lightning converter I have seen work in a Murano for its interface, so this should work fine for any lightning Apple device. That way you have the option to purchase one new as the Lightning connector is all Apple offers for new iPods.
2) look for a used iPod on ebay that uses the traditional 30-pin connector.
My recommendation for any iPod is a Nano. I like the size of it and the flash memory. The only problem is with older ones you cannot get much more than 8GB of storage. I believe the newer ones that utilize the lightning connector can go up to 32GB.
My other question for you is this - do you have the technology package in your G (navigation?) If so, it has streaming bluetooth audio, and you can get the latest iPod nano and stream everything over bluetooth, but I'm not sure that you can utilize the onscreen interface that way. Another option, though.