You have to get it from third-party websites. Unfortunately, Apple does not provide download links for macOS dmg file. DMG disk image is the only available option to create a macOS bootable USB on a Windows PC.
The first option is ideally to be used on Mac and the latter option is mainly designed for PC users who want to install macOS Monterey on a Mac or PC. To make a bootable macOS USB drive, an installer app or dmg file is required.
Part 1: Direct macOS Monterey DMG Download links Create Bootable macOS Monterey USB from DMG File
