I figure you may have already sorted this but I came across the same problem this morning and absolutely did not want to have to upgrade to 18.04 in Mint. Version 415 was as far as the repository would go. It's a bit of a pita but you can install a 16.04 418 driver manually within the CLI with some tweaking.
I used the following steps after bastardising several guides I stumbled upon. There'll be further detail required to update current build and download the driver if you're not using a GUI.
Update current Linux build
Use a browser to download the latest Nvidia driver from Nvidia website – currently 418.56 for Linux – save to download folder in home directory
sudo dpkg --add-architecture i386
sudo apt update
sudo apt install build-essential libc6:i386
Revert back from using currently installed Nvidia driver to using Nouveau driver. This is straightforward in Mint GUI but IIRC was more of a hassle in Ubuntu.
Disable Nouveau Nvidia driver:
sudo bash -c "echo blacklist nouveau > /etc/modprobe.d/blacklist-nvidia-nouveau.conf"
sudo bash -c "echo options nouveau modeset=0 >> /etc/modprobe.d/blacklist-nvidia-nouveau.conf"
sudo update-initramfs -u
Stop Desktop Manager:
Hit CTRL+ALT+F1 and login with your username and password
sudo service lightdm stop
sudo init 3
Install Nvidia Driver:
To start installation of Nvidia driver (replace download location as appropriate)
sudo bash NVIDIA-Linux-x86_64-418.56.run
I'm sure there's an easier way but, ho hum, it worked.