You have to search for 18.10.0 installer, the exact name of the file you need is:
epic-games-launcher-18-10-0.msi
Epic does not provide this installer anymore so you have to risk your system security downloading it from a third party. That installer does not auto update the launcher to v19.
More than a month ago I created a petition on this forum requesting an official link to an installer that does not auto update: