The factory no longer have any OEM wheel bearings available. The original source seems to be from a Fiat Limo but they also seem tough to find.
It was suggested that a Mazda MX7 bearing would fit but this has been succesful for some and not for others.
SKF VKBA 3683 is a bearing for a Citreon C5. these should be plentiful and are the correct size. I have not fitted one to my car yet so cannot confirm but it would seem worth a look.