Hi panda phil,
The 500 is primarily based on the Panda (2003-2012) model; the new Panda 2012 onwards shares most of the same bits still, but it has got some revised parts.
I agree that parts for the Panda 2012 model are hard to come by at times; I found that was the case before when we had ours.
Have you tried contacting shop4parts for example? They are really good to deal with and have always answered my questions without any fuss. If they don't stock what you need they might be able to offer suggestions.