Operation… Oboe?
These emblem variants can drop once you reach a certain score threshold in a Nightfall. The drop rates are unknown, but if you are looking to get this variant, you'll want to go for a high score run (get the highest score possible) in the related Nightfall, then do speedruns of the Nightfall until the emblem variant you want drops. Note this is a variant of the emblem named after the Nightfall it drops from.
