or this you'll need a purple item in all possible equip slots:
(this will require you to have all of the weapon slots unlocked. Also, purple items are not to be confused with PINK E-Tech items.)

- 4 Weapons
- Relic
- Shield
- Grenade mod
- Class mod

It doesn't matter what level the items are. Some general tips are to stash any purple item you find until you have all those required and to farm the BNK-3R boss as he will usually drop a few purples. The rarest one to get is usually the relic but with persistence, it shouldn't take too long to get one. If you have a friend who has some (or all) items your missing, you can trade them back and forth.
(It should also be noted that bringing over a saved character from your 360 file with enough purples to fill each slot would be the quickest and most simple way. If it doesn't pop right away just remove one of them and re-equip it.)