There is no Pokemon injector via the Homebrew Launcher currently. I'm not sure that it would be possible to make one. How the spider exploit works is that it edits your RAM, which means you need to already be playing the game for it to work (the game needs to be loaded into the RAM). Since you can't have Pokemon and the homebrew launcher loaded at the same time you definitely can't accomplish this via RAM editing.
The only other option would be to decrypt the save, edit it and re-encrypt it. In theory this could work, but somebody would need to figure out how to make what is essentially a homebrew version of SaveDataFiler.