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.
Digikey. Below is a URL but I don't know if it will get mangled or not. Search there for "nylon standoffs". You'll find them under "Board spacers, standoffs".
Sometimes I can find them on Amazon as well. The knurled thumb screws I got from McMaster-Carr. McMaster-Carr also carries standoffs / spacers, but charges too high of prices for them.