1st Yes, there is a worldwide GPU shortage, and yes it is difficult to buy them right now. But you can actually find them if you know where to look. I just bought a 1080ti yesterday for $799 from newegg. And from what i've been told if you have a massive order of 50+ 1080ti GPUs you can call directly to a manufacturer and make a private order.
Good Luck
Nvidia Wants To Fix GPU Shortage By Asking Retailers To Limit Sales To 2 Per Customer.
Nvidia Calls for Limits as Crypto Hysteria Pushes GPU Prices Sky High
There is a few more article about the current nVidia vga cards situation