In their typical fashion, unless you know what you're doing, Microsoft made it incredibly difficult to get your hands on a simple basic executable, that they should by all means provide as an easily accessible download, since it's one of the basic brick to try and safeguard a Windows platform.
Well, we know what we're doing, which is to use a very handy technique that we picked up from actual malware, so, from PowerShell:
curl.exe -L -A "Microsoft-Symbol-Server/10.0.0.0" https://msdl.microsoft.com/download/symbols/signtool.exe/910D667173000/signtool.exe -o signtool.exe
