Slingshot
thingiverse
I threw together a rough outline of what I was thinking. Take a look and let me know if it's up your alley, because odds are good you'll want to tweak the scale.
Download Model from thingiverse
With this file you will be able to print Slingshot with your 3D printer. Click on the button and save the file on your computer to work, edit or customize your design. You can also find more 3D designs for printers on Slingshot.