Definitely never seen this before! Do you have the original product listing? I’ve been trying to include links to those in the gallery to things not listed on Bricklink or Brickipedia for general reference.
Working on this makes me really wish we had a comprehensive list of merch since there’s so much random stuff–I asked a friend at LEGO if he would be able to get one, though he was skeptical he could share it publicly. But I guess we just have to treasure hunt.
Thanks for the reminder! I have it saved on my computer or open in a tab somewhere, along with the the bedsheets. There are a handful of miscellaneous items that I haven’t been able to get up just yet–I’ll try to do that in the next couple days. 
Thanks for the catch–There is an ungodly amount of BIONICLE bags and backpacks which don’t have known product listings. That must be the same as this one. Not sure if the smaller ones are the same as the ones in the gallery or not…
I mentioned earlier that there are some items I just haven’t been able to track down, and here’s one: There is a mysterious Gali hat that has been spotted floating around, and apparently the other five Toa had some too. More recently an Onua one surfaced, but the other four have proven elusive…
https://www.reddit.com/r/bioniclelego/comments/1ddp2er/help/