Is the Fiat Pop (or its engine) available in N. America?
I've experience with my 2 B5254S Volvo engines.....and a few others.
OE is always a choice.
The 'triumvirate' of foreign filters....Mahle, Hengst and Mann.
Back when foreign cars made up the bulk of element filter sales, it was easy to conclude the filter companies were simply price gauging.
"How can an oil filter without any valving or external can be more expensive than any spin-on?"
I concluded it was because, a) they can and b) they have to use stronger material as the customer can feel the element.
I noticed the 'approved' filters for my car, Volvo and the ones mentioned above, were always quite hard to the touch.
Certain aftermarket brands used a "fuzzy coated" element.
NOGO on the soft & fuzzy versions.
What I'd do were I in your position is get an OE filter. Note whatever you can and match any other replacement against it.
Go with any that look similar.
Without spending on science or measurements, it's the best you'll be able to do.
If it becomes torturous, stick with OE.