Dealer who sold it or factory, which ever is closest to you. Have them fix it.
Of the things that are known to cause rattling from the side entry door, the pull down shade... Should be kept down, across the door window when driving. The door adjustment, are all the screws on the inside of the latch cover tight? Are the latch screws in the edge of the door tight? And last.. You should make sure the door is fully closed by keeping the deadbolt extended into the striker plate while driving. If the deadbolt doesn't easily extend into the striker, pull in on the door to see if you hear the latch click in place, then try the deadbolt again.
