I tried to scrounge some dust caps a while ago and it didnt work! they are hard to come by.
When i refurbished my front uprights i fitted new wheel bearings and i destroted my dust caps getting them out as they were badly corroded.
So i went to my local ford who had one in stock but couldnt order me another as he said they cant get one as they are discontinued. He apparantly tried all the other ford dealers stock and nobody had one.
A couple of weeks later he rang me saying he luckily found me another
So ford is prob your best bet if you find someone who is genuinely helpful they may be able to get you one. They were only about £3 each.
Good luck