I'm already trying to get villagers that sell mending books, believe me. Just asking so I don't have to gamble with villager luck.
I suppose I can be more helpful. https://empireminecraft.com/threads/selling-mending-books.65107/ Not sure if any are still in stock or if you have checked there already. But I got a villager on my first try of placing down about 20 librarians, so I suggest you keep trying!
They are sold on 12221 and 12220 for 700r each - go to /v 12221 tools and then to neighbor section on 12220, or go to /v 12221 armor and go to the nearest corner.
Hmm, guess I should chip in too 3544 top floor also sells mending books, and I think you can always ask Aya in PM for some kind of deal