Can't help here, never had hubcaps that stayed on long enough on any cars. But you can try this:
http://www.fiat500owners.com/forum/...um/11-fiat-500-wheels-tires-suspension/20273-baby-moon-hubcaps-do-yourself.html

 

Everybody has this problem. I see 500 hub caps all over the road and there aren't that many 500s!

The design is flawed, and can mimic a bad wheel bearing with squeaking and groaning when going around a corner before the hub cap flies off.

Forget about a recall, just man up and get a set of alloy rims.

Don't be a girl and just whine about it!

TEdolph

 

Lots of issues with the Pop’s wheelcovers. Really a bad design. Fiat will never recall that. That why, all the newer Pops, now come with alloy rims.

You might buy consider buying some aftermarket 15” wheelcovers, from Walmart, or a Automotive parts store. Another option, buy some salvage OEM alloys. The Tirerack, carries a wide selection of after market alloys for the 500. I’d go from 15” to 16” rims. Lower profile tire.

 

Smark's advice is good. Second hand alloys, even OEM's are not very expensive. Maybe $100.00 each.

tEdolph

 

Since I have steel wheels for my winter tires, I have inspected my hubcaps for proper retaining wire routing.
It is very easy for the retaining wire to lay on the wrong side of the plastic tab. When that happens, the whole tensioning force is loosened and is noticeable after installing them. At my last swap, I had one that didn't look quite right, and sure enough, the wire wasn't in place.

 

Also, the more you take them off, ther looser the plastic gets...I bought a new oem set and ther tension was night and day...the old ones could be removed very easily, the new ones are very snug and I use a plastic tool to gently lever them off...