The creator of the Rufus USB tool maintains a script that pulls directly from Microsoft's legacy servers (which still host some old ISOs via Akamai CDN).
Windows Small Business Server 2011 Standard - Internet Archive microsoft windows small business server 2011 iso download
Unlike Windows Server, SBS 2011 requires you to run Setup.exe only from within a full Windows environment (not booting from the ISO). You must: The creator of the Rufus USB tool maintains
Finding a is possible, but it is no longer a click-and-run operation. The safest path is: microsoft windows small business server 2011 iso download
Instead of hunting for that ISO, consider these modern migrations:
Before you spend hours downloading a 5GB ISO, consider that SBS 2011 is a security nightmare. It uses TLS 1.0 and SMB 1.0 by default. Here are better alternatives: