I bought this one
Xtorm AL390 Laptop Power Bank 18.000 (Schwarz, 18.000mAh, 220V, AC, USB)
Connected MD and OT to it and had it running for more than 90 minutes before turning it off..
At that time it had about 75% of energy left.
It makes only a little noise and it did not get too warm.
Next time I will connect my iConnect Audio 4+ as well and see if it holds long enough with the ipad and a Korg nanokontrol2 connected to it..
In my case I would be happy to have power for one hour or two. That would be enough