Domo Pad6 key macropad based on the same circuit as the 6 Pack, and runs the same Arduino script.
Two PCB's are used, one as a base. The PCB is under 100mm x 100mm, you can order 10 for $2 from Easyeda.com. DHL shipping is another $18, airmail is cheaper but can take over a month. You can have only one $2 special per order. Additional 100mm x 100mm PCBs are also discounted to $5 for 10, which is still very cheap.
File on github.
Switches were rotated 45 degrees. Looks weird but it works fine.
I trimmed the leads on the socket flush before soldering so that they would stick out as little as possible. M2 spacers and screws. PCB mount switches required.