I looked around for boot knife for quite a while. I am an old time biker with the following boot knife requirements:
a) The knife had to pull down to pull from the sheath. Not lift my pant leg to reach the handle.
b) If you don't wear tall boots, your selection is very few to find a down pull knife that does not show when you cross your legs or sit on a motorcycle.
c) The best boot knife I have found, with these qualifications, is the CRT Bear Claw. It is quick to pull, small and quite aggressive looking. Also it is cheap enough that you don't care if it gets wet, snowy, or muddy.