The search for a is a journey into abandonware. It is technically possible, legally gray (but ethically acceptable if you own a license), and practically risky. If you choose to proceed, use only verified sources like the Internet Archive, verify the SHA-1 hash, and never—ever—connect the final installation to the internet without a firewall configured to block all inbound and outbound traffic except to trusted legacy networks.
However, there are still some options for users who need to download a 64-bit ISO image of Windows Vista Home Premium: Windows Vista Home Premium 64 Bit Iso Download