This is the question under discussion:
I would interpret this question as being on-topic based on this item:
Martial arts equipment (including use, maintenance, and construction)
I do not see any current item on the do-not-ask list to counterweight the on-topic portion.
Although other StackExchange sites may restrict shopping or recommendation questions like this, each site is expected to maintain its own question standards. For example, recommendation questions are off-topic on StackOverflow, but there is a separate Software Recommendations site that accepts recommendation questions that meet certain standards.
The fact that other StackExchange sites restrict shopping and recommendations questions does not mean that martial arts should. Shopping and recommendation questions for technology equipment quickly go out of date because every few years models of mobile phones and laptops become obsolete. Martial arts equipment does not become obsolete every few years.
To me, this question seems very similar in character to this other, better-received question:
Although past questions are not necessarily indicative of what is acceptable now, we at least need to explain clearly what is acceptable now.
Similarly, Philosphy and history of Okinawan Karate is a shopping question. I think this is fundamentally a what question. The answer should be a book title with author and publisher and description of what is in the book. The asker can go find a seller for this title themselves.