[camatz01]

I believe you can take fused power from the A pilar. Search for the pdf install file of part number BCKA-V7-210. It is the auto dimming mirror and in the pdf includes how to get power for the mirror for models without it. That could work.
Googling “BCKA-V7-210 pdf” I found the manual easily

 

[camatz01]

Hi guys.
I've just bought a brand new CX-30 a week ago and faced the same problem. What about buying a USB connector with wire (like this) and using power as ACC? Yes, it also requires laying that cable from a central console to the fuses box, but it can be under the driver's seat. So I guess in this case parking more should work.

I took power from the rear view mirror. Is ACC controlled and there are adaptors that are plug and play, are concealed and give you an usb (5v) connector (Dash Cam Install Easy as 1..2..3..). If you need 12v, can be done by modifying the connector (Just getting the power from 12v and ignoring the 5v circuit), or just go to the mirror harness and take power from 12v wire.