Thanks!
I have Identified the Grand Inquisitors' boots. They are Tuff rider brand Equestrian boots. they have the same tongue, spur rests, and unique details. There is a stretch panel in the back of the boots along with a zipper. I created a collage of my findings below. These are not standard or ordinary riding/officer boots. Though I can see officer boots being a basic approval, any higher must use these. There are some modifications such as the top strap being removed and the Spanish head style at the head of the boots has been removed/cut off so the head of the boot lays straight and flat instead of curved. Initially, I was puzzled about the use of a stretch panel, but then recalled that we started seeing them on Imperial officer boots in the Mandalorian Season 2.