Vatican souvenirs - where else to get them?

You may not be able to buy 'souvenirs' with Vatican stamped on it, but you will be able to buy the same sort of souvenirs in most Catholic cathedrals in Europe, and often in monasteries that are open to the public. They will often have a little stamp of the place you buy them. So you will have to explain your relatives why you did buy their souvenir in this special church for them.