I'm not super happy with this one, but when it comes down to it you might have to fiddle around with just about any solution that's given to you. It's kind of the nature of procedural generation, so here goes.
This is based on another answer I did over here:
Sine wave on the environment texture
You can read through that for the whole discussion on this. Here we do a Y Wave Texture influencing an X Wave Texture, and then reverse it to get a 90 degree rotation. Then we add those two together and use it for the Alpha channel.
For this primitive plane, the scales should always be around the same (but they don't have to be exactly the same) and the Mix Factor controls the height of the wave. So it should always be very close to 1, but how close depends on the scale of the wave textures. You'll have to mess with them to get it to look right depending on the size of the mesh it's applied to.