@pinbi7 is correct. An RCM Loader is readily available and provides the same result.
If you want to build your own…
I’m pretty sure the dragon injector was just a SAMD chip, so a Trinket M0 is pretty much the same thing. You can build an external injector with a Trinket OR you could solder the Trinket inside your Switch and and never have to “inject” anything manually ever again (you’re still injecting…just automating and hiding it inside your Switch.)
you can absolutely fuck your shit up really badly. This shouldn’t be your first soldering project. Some of the solder points require a microscope and you‘re often literally millimeters away from other things you don’t want to melt and float away. You’ll laugh, you’ll cry you’ll experience all sorts of emotions but it’s a really cool mod once it’s done!
Bought a used Nerf Mega blaster yesterday, good condition, but only got one single foam dart for it. And it was so chewed up, when I tried to fire it today it ripped the tip clean off and spat the thing out in two pieces.