The progress made by the guys these last months is impressive, and both the UI and hardware aestetics really shines (while they are inspired by the OP1, they now have their own personality)
Axoloti:
(There are great cases/knobs/button boxes for this, for example check this thread out for the mad directions things can take: https://www.muffwiggler.com/forum/viewtopic.php?t=158092)
Organelle:
https://www.critterandguitari.com/organelle
Another very cute, very programmable portable digital synth ..
And then there are things like this, which I had the pleasure of playing recently at superbooth:
Sonicware ELZ1:
https://www.sonicware.jp/elz-1-1
So, yeah .. lots of little portable, digital and analog synths in the OP-1/-Z style format.