Once upon a time....MAC had the perfect light grey shadow called ISSUE, my absolutely favorite EVER!!!
I've bought at least 20 shadows, trying to dupe it, so here are the ones that have come closest:
Shu Uemura - M950
Rock and Replublic - Ciggy
Illamasqua - Soul ( silvery )
And finally MAC recommended using - Vanilla e/s as base with Scene e/s over i.... That combo is quite nice

)
HTH