iShark cord wrap
thingiverse
Shark cable wrap for an iPhone block and cord is what you're looking for, and it just might work with some aftermarket chargers, but trust me, it was designed specifically for the OEM one. I printed mine face down and used supports, so if you give it a try, please post some pics so I can see how yours turns out! Enjoy! Update: I took it up a notch by adding a version 2 of the iPhone cord wrap that boasts an even stronger tail section, and I didn't stop there – I also whipped up another version for iPad chargers.
With this file you will be able to print iShark cord wrap 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 iShark cord wrap.