Hello,
A couple of months ago I've bought myself such a bluetooth adapter on aliexpress:
for a non-FIAT car, but as you can see on the top of the photo, there are also ones that will work with FIATs. In fact, everyone will, but if you buy a dedicated model, the plug (in this case the yellow one) will fit perfectly in the car socket and the cables will be correctly placed.
There are version with microphone (as this one), or without, depending if you want to use the car audio as hands-free set.
The sound quality is good enough for a car. They cost like 5 - 10 USD shipped.
Try looking with 'fiat bluetooth adapter'. Be sure you choose the correct one (that will suit the Punto Evo and an iPhone).
It requires taking out the original radio and wiring the +12V and the ground cables.