Ok so earlier in my adventures i happened to sell my nightingale armor due to me planning to use the Guild Master Armor instead (I kept the boots however for the muffle enchantment)

I now however wish to try and use the nightingale armor instead however the merchant I sold it to no longer has the armor.

So my question is this, is there any way to obtain a second set of Nightingale Armor? I've tried reverse pickpocketing Karliah to no success and tried using the armor stone in nightingale hall but still nothing

Any help would be greatly appreciated

There's two courses of action here: reload a save from before you sold it or start a new game.

Are you on console or PC? I think there's no way to get it on console, but there may be a PC console command you could use.