Microsoft's Surface has the perfect aspect ratio for screens (3:2), imo. Wide screen devices just look wrong. 16:10 is fine, but it still isn't quite right (this is also what Apple uses.)
I think this was it: https://www.amazon.com/Lenovo-ThinkPad-Thunderbolt-40AN0135U...
I bought one to use with my HP work laptop at home.
Dock works perfectly, cannot say the same on other Dell docks (TB15 and some other).