On my recent trip abroad I had a tag axle wheel bearing go on my 1996 B694.
I managed to limp home with it by slightly over inflating the adjacent wheel and thereby taking some of the weight off it.
When I got home my service man managed to get the new hub and bearing assembly fairly easily and quickly through the local Fiat agents.
Hope this helps,
PS Could I suggest that this is a topic for the Hymer technical section and maybe it would be interesting to find out what the incidence is of tag axle failures?