Need help for windows 8.1 iso download 64 bit and 32 bit

My laptop comes with Windows 8.1 and it couldn't boot into desktop anymore. I need to make a bootable usb drive but don't know a safe place to download Windows 8.1 iso image.  I need both the 32-bit and 64-bit versions. Can anyone share a reliable place for windows 8.1 iso download? Thanks