Parallels International Gmbh don't link to previous point release for their software which makes it difficult for those who happen to find themselves at the whipping end of their QA team's failures.
So if you're after a particular version - for me because updates keep breaking Parallel Tools in so many weird and wonderful ways - you can get a specific point version using the following URL format:
https://download.parallels.com/desktop/v19/19.4.1-54985/ParallelsDesktop-19.4.1-54985.dmg https://download.parallels.com/desktop/v20/20.1.3-55743/ParallelsDesktop-20.1.3-55743.dmg
The specific versions and build numbers can be sourced from their updates pages: