Just a quick suggestion:

Before you start to assemble your i3 printer frame, take the pieces that make up the extruder mount and the top piece of the X-idler where the Z-axis end stop switch actuator screw goes through.

Put then on your document scanner, in the centre of the scanner be, and scan them. Save the scans as jpeg files.

If you need replacements at any time, you can load the jpeg into your CAD program and draw up a new part by first making a 2D drawing by tracing over it with the polyline tool, then extruding the 2D drawing vertically 6mm. Then save as an stl file and away you go!

Old Man Emu