I use a USB-PD power bank with a trigger cable which I bought directly from China: UsbC-zu DC5,5x2,1mm 9V 12V 15V 20V Trigger Power Kabel für LCD Monitore Cine Broadcast Radio 9V 12V 15V 20V DropShipping - AliExpress 7
Since 12V is optional in the latest version of the USB-PD specification, make sure your power bank supports it.
In order to make sure that I always have 12V available no matter how the spec changes and what power bank manufacturers decide to implement in case I have to get a new one, I also got myself a “DIY USB-PD power bank”. It has a 12V output and can be equipped with 18650 cells. When the cells break, I can just replace them.
Example (the one I got is not available at Ali anymore): 4x18650 DIY Power Bank Fall Tragbare 18650 Batterie Ladegerät Lagerung Box Digital Display Schnelle Lade Mobile Power box Für Telefon - AliExpress 44
I don’t have any issue with RFI on any band of my QMX+.
73 Jens HB9EKO