MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
Filaflex is currently the most flexible filament for 3D printing, available in 1.75mm and 3mm diameters.
It is made by Recreus which is a Spanish company so that will be the reason for not so great English.
You can find it for sale here : http://www.recreus.com/en/http://www.recreus.com/en/
For this design, other flexible filaments can be bought, i.e. NinjaFlex, Arnitel, and Makerbot also sell a flexible filament too plus others no doubt. Their properties will vary across the manufacturing range so you may have to adjust the infill density to get teh flexibility you desire.
Hope this helps,