In GIMP any graph paper can be made transparent so you only get the grid by adding a Multiply blend mode to the layer its on to make all the white on that layer invisible. I am assuming that this is also possible in PS?

If the lines are too faint to make a mark, you just duplicate the layer a few times till they're right. Then hide all the other layers and make a new one from what's visible, and discard the rest of the graph paper layers.

Using that technique to make things transparent, you could use any of that paper from the second site ChickPea linked to above.