I was really excited after coming across the Keybiner kickstarter (link: https://www.kickstarter.com/projects/fortiusarms/keybiner-the-carabiner-refined) and I did a backing that would get me an aluminum keybiner. I couldn't wait until the couple of months estimated for the delivery to try the idea out-- so I made my own version that you can 3d print or laser cut.
This design isn't perfect by any means-- the printed clip doesn't have very much tension, and I didn't spend much time designing a useful hole pattern in the middle the way the real keybiner has (although the largest hex shaped hole is sized for screwdriver hex bits). If I have more free time for this (ha!) the next revision would probably have an integrated clip like the one shown here: http://www.thingiverse.com/thing:169192
I used 4-40 screws with nylock nuts to hold it together, 1/2" is just barely too short for 2 keys depending on the thickness so I would try using a 5/8" length screw.
I've included an stl for the spacer I used, although it hasn't been tested because I just used a nylon spacer that I had. The .stl has the same dimensions as the spacer I used and works well for having two keys.
There is currently no version of the clip that can be laser cut, so you will either need to 3d print it or fashion your own if going the laser-cut route. I originally made the hole sizing to fit wire off a coat hanger, but wanted to make a solution that you could also entirely print. I've also used a piece of raw 3d printer filament (1.75mm) and bent it into shape and used a soldering iron to melt the ends to prevent the filament from coming out. This wasn't as stiff as the printed clip though so it might not be what you want.