I printed out several of jgr526's great NS Grip designs. I found v1 and v3 to be too hard to reach shoulder buttons. v2B is too slim and less grippy. v2A is perfect. There is however one problem---the model is mostly split in two halves; see the slicer image below.
I left comments but the designer seemed to have ignored them. So I fixed this issue with Meshmixer's Make Solid function. I also extended the bottom holder to also catch the tablet, otherwise it's held only by the joycon's locking mechanism and will wear it out. Finally I tilted the model backward by 30 degrees and cut away 3mm of the bottom so now it will stand at an angle as well as upright. The angle is perfect for viewing when standing on a table.
The original size is slightly too large. Scale x (and only x) to 99.3% for a loose fit (or tight fit when applying electrician's tape to the sides which I recommend, so they don't scratch the joycons). Scale x to 99.15% for an exact fit without any tape, and 99% for a tight fit.
The original designer does not allow remixes, although I do not consider this a remix (it's identical in design) and believe it benefits the community. If jgr526 is reading this and wants it removed, I will happily offer my fixed version to be included on your Thing page.
Print in PLA at 205c for a strong layer bond. Be sure to use brim and support (65 degrees everywhere will do). You may need to rotate it to fit on your bed diagonally. Remember you need to scale x before rotating it.