The part that comes over the MX stem is purposefully a bit too large because my RepRap printer is not very precise, so you will probably have to stick a bit of tape in it (that's the yellow thing in the third photo), but the part that joins with the Lego piece fits quite well. I have included a skp file if you want to mess with the sizes. The file was made combining the adapters made by u/THEonlyMAILMAN for the Reddit mechanical keyboard community and a 2x2 Lego piece from Thingiverse. Update: I have now also added files for a piece that fits tighter on the switch (lego_mx_smaller). You can try printing this one if you have a more precise printer. Update 2: I added a piece that uses less material and small groves on both sides to better fit Cherry MX Blue/Green switches that have a nub on the slider (lego_mx_lessmaterial). It still uses the MX stem from the original file.