There are several ways to find the installers you need for your Redgate tools.
Log in to the customer portal
You can access the details of your Redgate licenses by logging into your Redgate account on our website.
On your supported products page, click on the tile for the product you wish to install.
You'll find 'Download latest version' above the usage list.
On your invoice
When you purchase a Redgate license the download link for the installer is on the invoice.
On the Redgate download site
You can find installers for all the product versions you require, current or older versions, here:
https://download.red-gate.com/
NB: If you're looking for Redgate Monitor installers they are under https://download.red-gate.com/checkforupdates/SQLMonitorWeb/ not SQL Monitor.