Remember that Amazon is for the general public, not an specialist store. I often find it wanting in non- mass.produced, mass-demanded quality or specialist goods.
Regardless, that's why I took to always carry a flexible pocket A6 sketchbook and a small (say, 2000's-style) leather phone sleeve with several clutch pencils with various leads: so I can always pop it up and sketch something in a hurry (rarely have more than a few minutes to spare).
Notwithstanding, I have had a bad year for various overlapping reasons and have only made some odd sporadic sketches, so that is not a definitive solution either, but it does really help. That's one of my new year goals: restart the at least one 5 minute sketch a day routine.