Classic Parts of America (Chevy Duty) and Jim Carter (and others) sell these parts. If anything in/on our old trucks have been changed over the years, wiper blades and arms are at the top of the list (after oil).

1947-53 blade (10")
1947-53 left wiper arm (the left and right arms are supposedly different)
1954 blade (10" ??)
1954 left arm (the left and right arms are supposedly different)

Jim Carter\'s blades and arms look like those from Chevy Duty, but his '54 arms are 11" (sounds right to me)