Ammo counter for NERF darts, disks or foam balls, can be retrofitted into most blaster shells and scopes. This kit was created for modders that need an counter to keep track of their ammo.
Full overview and assembly video is available on Youtube.
You'll need an Arduino, a power source and a counting mechanism in addition to the AmmoCounter kit. I recommend an Arduino Pro Mini or Pro Micro.
You'll also need to setup a trigger mechanism (IR Beam or Lever Switch) and a battery source. These components will very depending on your blaster/dart setup.
Most of these parts can be found on the Sparkfun Parts List.
There is a working curcuit on 123D Circuits. It includes an IR beam, counter and reset buttons.
Yes, if you need a longer ribbon cable for your mods, you can use any "2.54mm Pitch 16 Pin F/F IDC Connector" ribbon from Amazon or local retailer.
Here are some suggestions:
The AmmoCounter uses a Common Anode 0.56 inch 2 digit 7 segment display. If you would like to know the dimensions, here is the data sheet.
Additional colors can be found on eBay, Amazon or by checking the AmmoCounter shop for updates.