I ended up buying two third party cases.
This one, from Aliexpress was ordered first, arrived second and is barely adequate. It is very cheap-looking unlined PU leather, and offers very minimal protection. It's only positive is that it is very slim.
This one, from Taobao was ordered second but (due to being ordered through an agent, as part of a larger order) arrived first. It has a solid synthetic fabric outer, a plush microfiber inner, and feels like it has some padding in between. It's only downside is that it's a tad bulky (about 23mm thick with Poke2 inside).
I'll probably use the latter when I need to put my Poke2 into a backpack or similar, and otherwise carry it unprotected (e.g. in a jacket pocket).