Getting some models to display correctly in Blender 2.8+

[notyoshi]

A lot of 3D World and NSMBU models use mirrored texture wrapping, where the texture is mirrored like this in the UV map:





However, Blender doesn't support this type of wrapping anymore, so the model ends up looking like this:





...which is obviously not right. I've been manually tweaking the UV map so it looks as if it was wrapped correctly, however sometimes this process takes too long or is way too tedious. Is there a way to automate this process or at least make it easier?

Edit: I am aware I could just edit the texture itself to be mirrored, but it's kinda hard to get the UV map in the right position. Also, I'd have to do it for every texture (normal map, specular map, etc)

[Joschka]

pingpong's a math node

[notyoshi]

Hey, that actually worked! Thanks!

Edit: Hold on, there's a small problem; a few seams have popped up.

[Sir Teatei Moonlight]

Edit: Hold on, there's a small problem; a few seams have popped up.

Seams like this happen because it's doing some blending with the pixels that are supposed to be outside the range of the face. I don't know if 2.8 has a better way to handle this but you can deal with it in two ways:

1. Tweak the UVs until it's far enough away from the differently-coloured block that the blending is no longer visible.
   
2. Disable texture blending.
   

You probably shouldn't be doing #1 on models you plan to submit; let the user decide whether that's how they want to fix it.

[notyoshi]

How do I disable texture blending?