ideal for shohin

I am not going to bore you with my personal views on bonsai pottery. So I keep it brief and point you to the references that are meaningful. This is by far the most insightful YouTube I watched about quality of clay and glaze to date: 

https://youtu.be/KgsoSudK14Q?si=e_wFv5O3SuOzxpIQ

Are you contemplating to baking boinsai pots yourself? NaoTokutake, a reknowned American potter recommends digitalfire.com and you will figure it out.

If you have taken the time to widen your perspective on what is optimal, and you are living in Europe, then have a look at the  quality and pricing of this Czechia's oldest and most reknowned source for bonsai gear.  You might understand why this is my favourite source of oven baked bonsai pots. 
(Hint: to view a pot in high resolution: RightClick -> "Open Image in New Tab".)

If you have a more refined taste, and you have a flavor for Europe's finest potters, why not have a look at https://europeanbonsaipottercollective.ecwid.com/ and source your bonsai pot directly from the artist.

There is more: a great resource courtesy of Angelica Ramirez https://www.arbonsaiart.com/european-potters.html 

Development Potting:

Develop Sekka Hinoki in low unglazed pots (e.g. Japanese terracotta pots)

Overwintering: 

Try to overwinter the Sekka Hinoki in a frost free place.  The trees that have overwintered free of frost will grow out faster and ealier than the ones that have been in frosty conditions.