After some research and a few tries .. I found a 12,000mAH battery that works and fits great in my Maestro and is available from Amazon Canada.
Power Bank, Lightning Power Bank®, Portable 12000mAh Dual USB External portable battery charger with LED display, Ultra Slim Aluminum body - sold by Amazon Canada, distributed by Lightning Power Bank. support@lightingPowerBank.com .. note I am not affiliated with the company at all -- I am just thrilled to have found something that works!!
will write a report as soon as I received the unit
73, de PE3DON
It may not be as high mA/hr rating as some of the other ones mentioned here, but at 2.4A output, auto-on, lots of 5* reviews and since it was available in Canada, very cheap (nearly 1/2 the price of the other ones mentioned here) and no shipping hassles, it was my choice. So far so good.
I see now the one you ordered.
I have the Polanfo Q5 Power Bank (among others). They have a LED display on the end of the battery. It shows % of battery remaining and is on when the Maestro draws current. I can see the display thru the slats of the back battery cover without removing the cover.