Thanks a lot, it just did not came to my mind to try a 2230 M.2, since MikroTik did not provide a mounting hole for that.
But then i had the idea to use a 3d-printed 2230-to-2242-M.2 extender , which is a better-than-nothing solution, tbh.
I did now order a 2230 M.2 (Kioxia KBG40ZNS256G).
Will report back here, if i can confirm that this particular M.2 works with the M33G, so other users have something they could relay on.
consider adding an additional mounting hole for 2230 M.2 to your products, since there is almost no market for M-Key 2242 M.2.
Except for the extreme expensive Intel Optane there is no M-Key 2242 M.2.
2230 M.2 are more available, since there seems to be way more demand for the smallest possible form factor than for the 2nd smallest.