Speaking of Ayamy, orders for her C106 stuff are now open on her Booth:
https://ayamy.booth.pm/
Orders are open until the end of the month, and ship in November.
If you don't want to wait that long, the artbook itself is available at Melonbooks for shipping now:
https://www.melonbooks.co.jp/detail/detail.php?product_id=3185460