This is not intended to be an exhaustive list, but I will keep records here of places with FP-friendly notebooks and paper supplies.

Stationery Shops

Soe & Soe

https://soeandsoe.com.au/

Ships from Australia.

Paper options for notebooks:

• Apica, Iroful, Kinmari, Logical Air, Midori MD, Midori Cotton, Nebula, Sanzen TRP, Seibundo, Yamamoto Takasago, Yusari
• Wearingeul:
  • Impressions
  • Nobile
  • Reservoir

Paper options for notepads & looseleaf:

• Lennon Tool Bar Egret, Iroful, Sanzen TRP
• Wearingeul:
  • Impressions
  • Reservoir
• Yamamoto:
  • Kin-Kaku-Den
  • Light Force
  • OK Fools
  • Sheeps Cloud Bond
  • Slight White
  • Smooth Art Paper
  • Smooth Onion Skin
  • Soliste
  • Takasago Bank
  • YUPO

Paper Shops

TarokoShop

https://www.etsy.com/au/shop/TarokoShop

Currently on hiatus, stocks notebooks in several popular papers (e.g. Sanzen, Iroful, etc) - worth checking when they come back online.

Danika58

https://danika58.com/shop/