I am using a GE headset. Sorry I do not have the model number as I bought it long time ago.
The ipod 4G takes a 3.5mm plug with 3 connections (stereo headphone and mic) and ground - so that is 4 segments. Most stereo headsets are 2 connections (no mic) and ground or 3 segments total - please take a look at one.
There is also a headset for cordless phones, but this is a 2.5mm plug (smaller than a stereo headset plug), and only have two connections - mono and mic. My GE headset/mic comes with the 3.5mm 4-segment plug, and has a connector that converts into a 2.5mm 3-segment plug for coordless phones.
For the ipod 4G, any 4-segment plug headset should work. If I plug in a stereo headset (3.5mm 3-segment), I can get audio but no mic.
Sorry I don't have the exact model number but I think you can try a headset if you have one or cn borrow one.