GPS to helmet communication for a dummy!!

[Pistol]

Ok so I have just purchased a helmet that happened to come with a set of ear pieces and a mike that the old owner used - said his blue tooth unit packed up so threw it away. How can I adapt this for use with a GPS for navigation purposes only - dont want phone etc purely to hear directions from the GPS - also need to know what GPS unit I need to get please???

Help a novice please :-\

 

[Esplin]