Exactly - In this case by tat I mean things like Harry Potter drinking flasks, Hunger Games calendars, and vaguely book-related trinkets that can be sold for under £5.
(The kind of high-margin items that you didn’t come to the shop for and most people won’t buy anyway.)
anything that looks cheap, is of low quality, or in bad condition:
Like most souvenir shops, it sells a lot of old tat.
https://dictionary.cambridge.org/dictionary/english/tat