IconSets is a set of web pages that I've created that make it easy to navigate shape sets created for Visio. I've used LINQPad to automate Visio to export icons from the actual shapes that have been created for various disciplines and technology areas.
The web pages are easier to look at than browsing through Visio stencils, plus they have a filter function that makes it even easier to find symbols.
Amazon AWS Icons https://visioguy.github.io/IconSets/aws/index.html
Microsoft Azure Icons https://visioguy.github.io/IconSets/azure/index.html
TODO: link to actual shape downloads on Amazon's and Microsoft's sites.