Some links to download Microsoft Visio stencils of the most popular vendors.
Amazon AWS Visio stencils
This page actually holds not only Visio stencils but other formats as well
Checkpoint happen not to have official stencils set, only Nokia appliances stuff can be found. So someone volunteered and using icons/press releases/PowerPoint presentations done by the Checkpoint turned it into the Visio stencils: fireverse.org
If nothing else helps here you can find the rest: