This piece is designed to be slid over the top plate of your printer and it has two pieces, one is designed to slip over the top of the rod, the other holds the bearing and slips over the top plate.
This requires one 608zz skate bearing (8mm ID, 22mm OD)
It should work with the stock screws, you just have to take a knife or some sharp object to poke out the screw hole. It is purposely covered to allow for better bridging.
Also, this must be used with some kind of coupling. If you just put the rod on the stepper shaft using the pre-drilled hole, the top of the screw may not be tall enough to use this design. I would recommend printing this as I have: http://www.thingiverse.com/thing:276192
I can only verify this will fit on a Two-up, but I believe the spacing between the rod and screw are identical for the One-up, so there is no reason it should work with both!