If you have a second controller and no other players available, this can easily be done on your own in the tutorial world.
Load up the tutorial world. Once you're in, connect the second controller, press the menu button and enter as a guest (or any other account you have available on your console). Walk up the stairs and take the iron pickaxe out of the chest in the room with the Enchantment table. Once you have it, take out your map and walk towards X: 9, Z: -34.
(Thanks to MTP Toby, he recommended these coordinates in his solution for 'Enchanter'.)
Dig straight down until you find the diamonds. Once you've mined them, make your way back up by using the cobblestone you've collected.
Now just make your way back to where you left the second player, throw some diamonds at them and you should be done.