Thunderhead Grips for Hunters are not in Ornaments
The 'Thunderhead Grips' legendary arms are not available in the ornaments section for armor synthesis. I have taken a screenshot of the 'Thunderhead Strides' for reference. I have also included a screenshot of the Grips being applied to collections.
There might be more, but this is what I've found so far.
Apologies for the required download of images, I'm not used to link-based file uploading. I tried to put them in the 'Image URL' bar, but it would not accept them.
Edit: First link was broken