As advice from a fellow backcard enthusiast, the Mountain Boy cards really don't come up that often, and when they do, they tend to be very expensive because everyone loves Mountain Boys...
You might also want to specify WHICH cards you want for ponies like Applejack, Tex etc that were sold in multiple countries, as there are multiple card designs depending on place of origin.
I don't think I have any of the ones on your list as a double, but when I go home I will check my folder.