Check Jelly Roll Fabrics, they mostly make up their own jelly rolls (20 strips) the basics page show a grey and then a yellow. I suppose it depends on how much you need or search the site a bit more and they may have the grey yellow combined.
https://www.jellyrollfabric.net/Basi...Rolls_c_8.html
found this too:
https://www.jellyrollfabric.net/Bena...l-_p_5117.html