The 4x4 has very different suspension at the rear, and is raised all round.
To do the job properly would ideally need the suspension components from the 4x4, as these are known to work. The manufacturer will have done a lot of R&D to determine the settings, anything you do may miss vital calculations. Researching the components needed will require a lot of effort browsing the parts listings, then more work sourcing them, perhaps from breakers, so a careful inspection would be required, then time and money fitting.
A used Panda 4x4 will provide all of this easily. Just might take a bit of searching, but they do exist. Just make sure it comes with a propshaft, as many seem to get removed to hide transmission issues. The centre bearing is replaceable, but not from Fiat, they'll only sell you a complete prop for over £1000.
Looking at your pic, it seems you have the steel wheels. Fit winter tyres. Either to those wheels, or source a set of spare steels. It'll probably be almost as capable as the 4x4, unless the snow gets very deep.
If you modify your car in any way, you must tell your insurance company. You suggest that insurance costs might be preventing you getting a 4x4, but I'd guess the increased premium for your modifications will be greater. If you fail to declare any modifications, you'll be uninsured.
I declared the winter tyres to my insurance company. They agreed it was necessary to tell them, but no premium change as it reduced the risk. Might have added cost if I'd used different sized wheels though. 155/80 13 winters on steels are incredibly good, although only had a little snow to test them in the past few years.