Not until you beat the final boss, and restart the game on NEW Game mode (essentially the new game+ of this game). You'll restart with Kirito's level, skills, inventory, and unlocked heroines' armor types intact, but the heroines' affection levels and equipments gifted to them are reset.
If you want every single LA Bonus item without starting NEW Game mode, you'll have to restart your PSP immediately after you fail to get the last attack on a boss. Otherwise, it's a miss for good unless the specific item can be gotten at upper floors.
Translation projects: Sword Art Online -Infinity Moment-, Mahou Tsukai no Yoru Ayachi's number one fan.