Small Triangular Pillow
Sold by Researching in Comfort. If you're as confused as I was: You need in silver quality to buy the pillow. The other "ingredients" are also greyed out, as long as you don't have all the correct ones.
The Small Triangular Pillow is a toy from Dragonflight available from a vendor that requires Spool of Wilderthread in silver quality to purchase.
Guide awaiting review
Obtain Spool of Wilderthread
Acquire a 
Spool of Wilderthread in silver quality, which is required to buy the pillow from the vendor.
Complete quest before buying
Turn in the quest Researching in Comfort before purchasing the pillow if you want to receive a free pillow as a quest reward.
Purchase from vendor
Buy the Small Triangular Pillow from the vendor using your silver quality Spool of Wilderthread.
