Milani Baked Blush in Dolce Pink is a great dupe.
This is literally the same shade as Orgasm. While it doesn't last as long as NARS, it still has good staying power and is pretty pigmented. You really can't beat it for the price. NARS lists Orgasm at .16 oz and Milani lists Dolce Pink at .14 oz so you are getting a tiny bit less, but really it's not a big deal for the color match and its 10 bucks compared to the 30 you would pay for Nars