This video shows the process of someone making a custom overlay for the LinnStrument using silicone rubber. This might be informative/inspiring to someone who wants to produce a custom overlay for the Sensel Morph. https://www.youtube.com/watch?v=i6gLo2d41Sc
Maybe you’re right. At the time I worked with clearflex we did not have 3D-printing (at least not that much) and we made our own molds, but I forgot the name of the material we used.