add factory bluetooth module

The first question I would start with is if your current head-unit is even capable of Bluetooth. On top of the module, you will need the mic as well. Pretty sure you can find the part on ebay though.

2006-2011 PRIUS BLU LOGIC BLUETOOTH HANDS-FREE KIT GENUINE TOYOTA ACCESSORY | eBay

In my opinion, you are better off getting a new head-unit with built in Bluetooth.

 

I personally use an aftermarket Bluetooth from Amazon and it does everything I want/need it to.

I have the entire thing wrapped up inside my center console plugged into my Auxiliary plug and 12v plug and have the circle mic on the side of the dash where my drivers seat is completely hidden away from view and it works like a charm. Simply connect your phone to it once and forget it's even there.

Works for phone calls and music without an issue at all.

EDIT: Pics of what it looks like in my car.