Latest Update 10/07/23:
Apparently Thingiverse is working on updating their website. Part of their new terms of service is all Things must have their 3d models attached, which is understandable. However they also say your account may be deleted if there is any violation. I feel that is harsh punishment for users, but as a sign of good faith and good faith toward the community, I have re-uploaded a selection of designs for these switch comfort grips. Hopefully Thingiverse will continue to improve for the better. Feel free to remix for your own designs and share accordingly! Have fun!

Update 05/01/20:
Unfortunately, I have been forced to remove my files from Thingiverse for these grips. Alot of people seem to not understand how licenses work, and seem to think they can sell my files and 3d prints of said files online. I originally posted here to share with the community, and encourage others to remix my design into their own design. Just because you put a new logo on it doesn't make it a new design. I congratulate others that have taken the time to remix my grips into something more that have uses or functions than originally I intended. I also apologize to people who cannot access these files anymore.

Update 12/06/18:
I uploaded an image to help resolve a few issues people are having. Sanding on the face of the rails will help if the joycons have too much resistance when trying to slide them on. See my previous update about extrusion multiplier. Also if you notice your joycons popping out too easily or won't lock at all, odds are the catch for your latch isn't flat. Sand the appropriate areas that are shown in orange and you should be good!

Update 06/13/18:
So after talking to several people online here on Thingiverse and elsewhere, I have been doing some tinkering and came up with a simple test print you can do to get your printer ready to handle the rails. After several test prints myself, I think what has effected me the most was my extrusion multiplier being set too high. For some reason I had set mine at 1.10 for something and forgot to change it back to 0.90, which is normal for pla. Takes about 1hr 23mins to print the test rails with my settings.

Update 07/01/18:
I intend to leave these grips on Thingiverse to share with the community (under a non-commercial license). However, I do run an etsy shop on the side so if you want me to print these grips instead of yourself, or you don't have access to a 3d printer, that is what the shop is for!
https://www.etsy.com/shop/NerdMakers
I will also upload designs not available on Thingiverse to the shop, so check it out if you want something new or different.

Background:
Been wanting a comfortable grip for the Nintendo Switch for a long time. Found several different ones other people made, but not exactly what I wanted.The closest thing I could find was designed by jgr526 (https://www.thingiverse.com/thing:2234489) but it was for using the switch in portable mode. Manabun also designed a pretty simple rail style grip (https://www.thingiverse.com/thing:2523187), however I had to sand the rails down alot to get my joycons to fit. I have used both and they are pretty great in their own way, so I decided to combine their two styles and make an all-in-one grip that fit my needs. Mad props to them for giving me the inspiration!

Edit 04/23/18 - Added Star Wars Empire and Rebel designs.
Edit 04/27/18 - Added Zelda BotW design
Edit 04/29/18 - Added blank template for anyone wanting to remix
Edit 05/16/18 - Added Overwatch design
Edit 06/13/18 - Added rail test .stl for easy printer tuning.

Notes:

• I recommend adding supports to the gap-lock area at the top of the rails and also adding extra supports to bottom of the grips to ensure a smooth finish. I have included my s3d support file if anyone wants to use it.
• Rotating the grip 45° on the Z axis when printing helped me at least for getting the first layer to stick.
• You shouldn't have to sand or trim the finished print other than remove supports. Just slide the joycons on the grip rails until they click and lock. Print and Play!
• To remove the joycons, press with on the back release button with one hand and use your other hand to push up from the bottom of the grip.

Here is a link to my joycon button covers: https://www.thingiverse.com/thing:2874433