If you missed some bonus rewards and want to buy it, you can buy them on Fantia or Booth.
The Booth only has recent 3 month's rewards and because Booth's rule is strange, the comics may be removed in the future.
Fantia :
https://fantia.jp/fanclubs/483836/products
Booth:
ζδΉεηι’ε€ε₯ε±ζΎε°δΊFantiaεBoothδΈοΌιθΏδΊηε―δ»₯εη¬θ΄δΉ°γ
BoothδΈεͺζζθΏδΈδΈͺζηοΌθδΈε δΈΊδ»ηθ§εεΎε₯ζͺοΌζͺζ₯ε―θ½θΏδΌθ’«η§»ι€
Fantia :
https://fantia.jp/fanclubs/483836/products
Booth: