As far as I know the TomTom can be used with any Bluetooth headset – I've used mine with a normal BT headset while using it in the car. There's no reason you shouldn't be able to use a small earbud type headset with yours. Infact the TTv1 shipped with just such a headset.
All you'd need to do is put the headset into "pairing mode" and then search for it on the TT.