Proxmox does not provide specific minor versions. The idea is that you upgrade all cluster nodes to the latest 7.x (currently 7.4-1, which you can find here: http://download.proxmox.com/iso/ ).
Wayback Machine is your friend [1], although this will give you v7.2-1, you may be able to install specific package versions [2] to match your currently installed packages. Still, as you've been told, the recommended option is to upgrade to latest 7.x and then to 8.x asap.