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.
An STL file can be gotten through the customizer. There is an "Open in Customizer" button on the lower right of the Thingiverse page. If you click this, you can type in the dimensions of your phone, and it will create a thing with an STL specific to your device. I've attached a diagram to this which shows what the various measurements represent (you can keep all other parameters as default).
When you create the thing, the "Publish" button is clicked by default. Please do not publish the thing until you have printed and verified that your dimensions are correct. At that point I encourage you to publish the thing with a picture, and your phone/case make and model in the title so that others with the same phone can simply use that.