Normal maps at -1 scale

I've just started experimenting with normal maps in my 2D game using the 2D renderer and lights. I've made them secondary textures in the sprite editor and they work fine at normal scale. When I 'flip' the sprite by making the scale.x -1, the lighting then flips up and down. Left and right is still fine. I need to do this a lot for when characters are facing the other way, so I'm hoping it's an easy fix?

 

This is a bug in Unity's sprites for which there's no 100% fix ... because Unity just outright calculates bad tangent data for sprites when they're flipped or negatively scaled.

There is a work around, though it comes with a (minor for most platforms) performance penalty. But won't work on all mobile platforms.
https://forum.unity.com/threads/get-objects-scalex-in-shader.847942/#post-5599693

 

That sucks. I guess I would have to do a version of that for the new 2D renderers shaders, and I don't have a clue about shaders. I'm running into so many issues using the 2d renderer with normal maps (it is experimental). Maybe I'll go back to the standard renderer and try a different approach. What's the standard tried and tested way of getting good 2D lighting with some sort of bump map effect?