3D-printing your own, or even trying a beer coaster, are other options.
One of the minor mysteries of the Surface Pro 4’s launch appears to have been solved: yes, you can now find a Surface Pro 4 spacer online.
What’s a spacer? Well, it’s been the answer to this question: If I own a Surface Pro 3 and a SP3 dock, and I wanted to buy a Surface Pro 4, would I be able to fit the SP4 inside my SP3 dock? Or would I really have to buy a new $200 Surface Pro 4 docking station, as well?
The answer to this question, has so far, been “No...but.” Although the Surface Pro 4 is nearly physically identical to the Surface Pro 3, a slight difference in the thickness of the SP4 means that the tablet doesn’t quite align with the SP3 dock’s connectors. As a solution, Microsoft originally said it would supply a free “spacer” to prop up the tablet and ensure a proper fit. Unfortunately, Microsoft apparently forgot to brief the employees at its Microsoft Stores, who had no idea what I was talking about when I asked about the spacer offer in the months following the launch.
Windows Central's Rod Trent appears to have discovered the answer, however: an online method to request that Microsoft ship you a spacer directly.
You’ll need to visit Microsoft’s Surface Online Support Center and click the “Replace an Accessory” button. Register your Surface Pro 4 tablet if you haven’t already. You should then see the option to have Microsoft ship you the free spacer. (Microsoft will reportedly charge $6 for shipping.) For some reason the serial number attached to our Surface Pro 4 wasn’t recognized as a valid serial number, probably because it was a review unit.
There are alternatives. A commenter on the Windows Central article notes that Microsoft has posted official instructions for 3D-printing your own spacer. Trent, meanwhile, suggests trying a beer coaster.