Variable output from Power Bank (24W = 12v * 2A and 5.4W = 9v * 0.6A)
You may want to consider using a standard 12V gel-cell or AGM lead-acid battery and charger for your 12V 2A load.  Ensure the charger can supply more than 2 Amps while at the float voltage output of (about) 13.5 Vdc.

This is far less expensive than using a custom Li-Ion battery and charger /with cell balancing.  As a bonus, you get far longer run time for far less money.

Consider purchasing your 12V gel-cell from an alarm company supplier.  In Canada, my alarm-company supplier sells 12V 8AH batteries for less than Can $20.  A suitable charger costs much more than that but the local automotive stores have suitable chargers.

If both units are located close to each other and can share the same power source, you can add a buck DC-DC converter to run the 8V device.