If you didn't have the Blue Flames (Eternal) and the Bungie Nameplate by Bungie Day 2011, then that ship has sailed, sunk, and is currently cuddling next to the Titanic.
There's no way to get them, OP.
...
But they [i]do[/i] look very nice on [i]my[/i] Spartan. :D
343 Industries manages all Halo content. Even if Bungie [i]really wanted[/i] to unlock these for you, they can't because they literally don't have the keys to this database. This includes, nameplates, blue flames, playlists management, stats and much more.