Solus currently has 340xx, 390xx, 440xx Nvidia drivers in the repo. Exactly like any other distro these days. There's nothing wrong about it. None distro has all drivers ever released by Nvidia.
It's impossible to install inexistent package(s) neither with DoFlicky nor with terminal. Your card isn't supported by 440xx series. It is still possible to install the closest lower release, available for the card - 390xx series. What DoFlicky correctly does.
An example. One of my computers has an old GeForce GT 555M. It is not supported by 440xx drivers. But it works very well with 390xx drivers.
Another computer has GeForce GT 750M card. It still works with 440xx. But not for a long time, I think for a year or max two. When Nvidia will release a newer drivers series, most probably it won't work for GT 750M. I will be forced to continue to use the "legacy" 440xx drivers.
