By 2017 Fiat stopped offering a TomTom unit (where the holder provided power to the sat nav), and replaced with a 'dumb' phone holder that has no electrical connections at all and is really just a rather well (over?) engineered plastic phone holder that fits most phone models, as it expands out to suit. You should have a a USB socket alongside that is there to power the phone. The 'Waze' special edition was intended to promote the free Waze app for Smartphones and worked (not too well!) with Fiat's rather pointless Panda Connect app (which basically duplicated the radio controls but further away than those on the radio itself). The part number is 735664419 but as mentioned in earlier replies they sell for silly money.
My iPhone fits well, and it's a good, non-wobbly holder that mechanically locks into the mounting hole in the dash. I use it for running Waze in my 4x4 (just as the app, not via Fiat's Panda app), powering the iphone from a neat, very short USB-Lightning cable from Halfords thats only about 100mm long.
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