There are three battle pets added in Shadowlands that are each purchased with 3 grey items as detailed in the followingWowhead comment.
Request to add these 9 items to the vendoring blacklist by default.

https://www.wowhead.com/item=186537/ruby-baubleworm#comments:id=5172753

Pet: Ruby Baubleworm
Purchased with: Ground Gear - Robble's Wobbly Staff - Very Unlucky Rock

Pet: Topaz Baubleworm
Purchased with: Rotting Bear Carcass - Dark Iron Baby Booties - The Stoppable Force

Pet: Turquoise Baubleworm
Purchased with: Rabbit's Foot - Large Slimy Bone - A Frayed Knot