I'm using a Arda Magnum Light Golden Blonde wig for Jack myself but the colour is much more golden in tone then yellow.
There also the Yuki wigs that are very nice colour for the Vessalius boys. there sold buy a few online sellers.
The shades is a tad less saturated then what you see on the screen. I ordered the Jack one but it doesn't fit my huge head so I hacked off the ponytail and added that to the Arda Magnum I have and hand sharpied some gold lowlight.
The colour it pretty close but the texture is deterrent and the two clip-on ponytails I tried to harvest the ponytail hair tangle like a bitch from Arda so this is my less then perfect option.
The wig is very dense however.