Transiting via Hong Kong might be one option, since the airport reopened to transit passengers on June 15, is easily navigable by a Chinese speaker, and is not subject to the same flight restrictions since it's not considered an "international" destination by China. And indeed, doing a quick sanity check on Google Flights, all available flights ...
Librairie Le Phénix,
72 boulevard de Sébastopol
75003 Paris specialises in Chinese books. Look at https://www.librairielephenix.fr/
https://fr.wikipedia.org/wiki/Gibert_Jeune has many choices as well and likely has Mandarin learning books. Call them to check.