While I do love notebooks of all sizes, for my work and research I prefer B5. It's a happy middle; A5 won't fit most equations in one line and A4 is a bit too unwieldy as my notebook has to share desktop space with a keyboard (mechanical of course), a mouse, other notebooks, coffee mug...
Currently I use the Apica CDS120S,
the Stalogy S4102,
and I am eagerly awaiting delivery of the Book of Ra.
As you can see all of them are softcover, and here's my problem: while there is a glut of slip-on covers in A5, there seems to be practically nothing in B5. Sure there is the LihitLab Smart Fit and the Kokuyo Systemic, but they are more like cases and way too bulky. Really, the only viable option I could find anywhere, after a considerable period of googling, is the Shachihata Opini, shipped from Japan.
Can this be it? B5 notebooks are not exactly rare, and pretty much all good options are softcover. You'd think acquiring a cover for one is just a matter of selecting one you like. Am I missing something? Is there a secret keyword that unlocks a vault of hidden gems? Can anyone suggest an option? I did come across plenty of standard composition covers, but the dimensions are off.