Glad you're happy, hope the car is what you wanted!
As for diecast models - good luck is all I have to say. Models of these little Fiats are surprisingly hard to come by - I've spent a lot of time looking (got a white one, so super common) and ended up getting it from America, and another from a small lakeside cafe randomly in the Lake District haha!
I'd keep an eye on eBay and so on, and might be worth asking a dealership near you.
I've seen a cabrio model version of the Yeye green 500, but never a hard top.