In Matt's video about unfolding the hypercube he made all 261 3D nets of the 4D cube out of mathlink cubes and he hand-numbered them. (The numbers are somewhere on the block with the raised dimple and match whuts.org numbering.)
To support the channel he is selling all of them! You will get one of the 261 original models, all of which appeared on-screen in the video (sorry, you cannot request a specific one). Each one comes with an authenticity card signed by Matt which gives you the model number and a picture of what it should look like.
Some of the models were slightly twisted during the filming of the video, or packaging after. You can use the authenticity card to make sure they are returned to their proper orientations. There may also still be bits of fishing-line attached to the ones which were hanging from the ceiling; you can choose to keep or remove it.
Please note that without very specialist equipment: these nets cannot be folded back into a 4D hypercube.