Hmm, from what I thought and could find on the internet right now, it seems that the original set of keys for a 2016 Panda was this one:
View attachment 472267
The one on the left having the immo, the central lock remote (with locking, unlocking and unlocking the boot buttons). And the one on the right is the purely mechanical 'spare' with immobilizer.
FIAT will charge you hundreds for getting a new remote key from the factory, but I'd still confirm with them that it is possible to add it to you car. I'm pretty sure that the remote key function should be available to activate via
MES, too.
The Ducato is using the same keyfob, I've asked FIAT for a spare like 3 years ago, they quoted me more than 400 EUR

(might even be 400 EUR + VAT, can't remember anymore). A locksmith offered one for like appx. 160 EUR. Programming and cutting the key included from both.
I've bought a
MES license, an appropriate interface, a chinese keyfob housing and the original Magneti Marelli precoded PCB board for the keyfob for around 130 EUR

And got the key cut for less than 10 EUR. Programming the immobilizer and the keyfob are two separate functions in
MES for the Ducato, but as far as I remember it's the same function for the Panda.
So I've paid less and still have
MES and the interface
The only problem is that there precoded PCB are no longer available. Probably FIAT stopped selling them some time ago, as anyone could do the same trick. A locksmith could just copy the existing data from the one you've got to the new one, but it won't be possible as you don't have the original remote keyfob. The guy I've bought the PCB from told me that it's still possible to do it, however some data (which cannot be read with
MES) from the ECU should be provided, so he could program (or perhaps only precode) the keyfob. The operation would probably be a little bit more expensive, but still much cheaper than what FIAT offers.