Originally, around 2014 I think, the Panda Cross was introduced as a ‘posher’ version of the 4x4. The Cross had 4x4 but they added Hill Descent Control, auto climate control and a few bits of extra plastic trim - including the silver and black side panels.
Wind forward a bit - 2018 I think? - and Fiat started the slow process of ‘killing off’ the Panda and clearing the parts bin. This started with the Panda ‘City Cross’, which looked like the ‘real’, 4x4 Cross, but was only 2WD. It retained the bigger door protection panels, but painted the colour of the car, not silver. Other ‘special editions’, such as the Panda Waze also came along to use up the bits too. They seemed to run out off the 4x4 and 4x4 Cross alloy wheels pretty quickly as they all got steel wheels with plastic covers from about 2019 too.
The 4x4 Pandas ‘died’ - 2023 perhaps? But still the parts needed using
Now, all the most recent Pandas have a real hotch potch of trim bits — they all have bumpers originally only used on the 4x4 version, for example — and the Cross name now has nothing to do with off-road (ie ‘cross country’) driving any more. The latest ones have a simpler trim panel (more like the original 4x4s, and not painted at all.
So - to the point: the panels you’ve seen were genuine Fiat bits. And only Fiat can supply them. But, there’s probably none left. Except via car dismantlers (breakers yards). I suspect the bigger panels fit the same holes in the doors as the ones you have, plus some glue. Start the search - there’ll be one out there somewhere. Search Panda Cross 4x4
(Sadly the copy of the
ePER parts catalogue on this forum is quite old, and pre-dates the Cross being introduced, so we can’t look up the part numbers…)
Edit… this link will point you in the right direction though! Note though that these bigger ‘Cross’ panels also used a different front wheel arch trim piece compared with yours
https://augustin-group.com/p/door-trim-strip-at-the-rear-right-7530184oe