I replaced the whole antenna mounting and antenna on my NV200 as I upgraded to a DAB radio. However, if I recall correctly, there's nothing particularly special about the thread on the original NV200 mounting i.e. you can basically use most generic screw in antenna. Lots of options on Amazon and Ebay, from bee stings to something like the original mast e.g. this.
I'd give your mount a good clean first though - looks like it has been missing for a while and the female thread has rusted.