Microsoft Continuum dock is the main selling point of Lumia 950 and 950XL users but if you were not the early adopters and missed the free HD-500 Continuum dock, you can simply get yourself a simple USB-C to HDMI adapter and Bluetooth keyboard with touchpad and save 100 dollars.
This has been confirmed by an XDA-developers’ member who said that aforementioned combo is working just fine. This Aukey USB-C to HDMI adapter retails for mere 24.99 dollars at amazon and does a fine job in offering same functionality as Continuum dock.
The only thing you will be loosing are the USB ports but at least you saved yourself 75 bucks.