Just a few quick hints if you want to build one:

• buy the Etekcity EL11 scale. I haven't tested it with other scales
  

• use a pair of pliers to unscrew the (glued in) luggage-hook (counter-clockwise :) )
• open the scale (2 screws in the back)
• unscrew the PCB (3 screws)
• unscrew the load cell (2 screws)
• unsolder the load cells 4 cables
• solder 4 wires as long as you need them (don't go too wild, maybe 50cm max or so) to the board. note colors and position!
• push wires through the opening in the case where the hook was
• put PCB back
• close case and tighten fasteners
• add heat shring tube to the wires
• solder your extension wires (in the correct oder of course!) to the load cell wires.
• shrink heat shrink
• cut M3 threads into the load cell case
• put load cell into the case (secure each corner with a dab of glue)
• put on lid, fasten with M3 screws

The hole in the lid is 8.2mm to account for shrinkage after printing. 8mm steel rods or tubes fit well.
I added the STL, STP and FreeCAD files in the files section. Happy hacking!

Misc

• the PCB has programming/debugging pads easily accessible, haven't bothered looking if the scale maybe puts out a serial stream like many calipers do
• the scale has a thermometer included
• you can add another hole in the bottom of the case to add the luggage-hook back. That way you can still use it for measuring hanging weights. (this will bu quite uncomfortable because of the small case though)

Cheers, Jan