I’m not sure if your buttons are supposed to work that way! Can you give a link, where you bought them and maybe there can be found any document with further information.
Many TonUINOs come with a powerbank-solution. So, no problem with that!
Maybe this thread https://discourse.voss.earth/t/an-und-ausschalter-anbringen/14673
can give you any hints. Even though it is in german, i’m sure you can find a way on the internet to translate 
Thank you. I’ll try my best with my limited German 
I have also found this link which is describes a few things nicely (the breadboard from AZ delivery came with that power supply module) TonUINO – Wikifab
And here the arcade buttons I have: Amazon.se
It depends on your power bank. Does it support automatic turn off when a device no longer needs power?
If you enable the stand by timer in the admin menu of the tonuino, does the power bank turn off after you pause the music and the timer runs out? (My power bank turns off about half a minute after that)
Thank you! 
@Gute_Laune My power bank never turns of. Could you please share yours and also, how do you get it to turn on after turning it off?
So, how do you prevent it from running empty?
Can you switch it off with a button?
If you make this button reachable thru your housing, you might use it to switch your TonUINO on and off?!
If I were you, I wouldn’t use mine.
Using the automatic turn-off of a power bank is „easy“ if it works. But it is not that reliable. The general problem is that you cannot influence at what power level it switches off. It’s built-in, and you have to make that work. For example, I need an LED to prevent my power bank from turning off while the TonUINO plays music. That depends on how full or empty it is. By controlling this LED with the Arduino, I can be more certain that the power bank will actually switch off when I want it to. But if you have a power bank where this isn’t necessary, it could easily happen that something changes and the switch-off function no longer works.
You also need an additional switch or button to be able to wake up the power bank. A button means you cannot turn off the TonUINO without waiting for the timer of the automatic turn off. When you use a switch and use the auto turn off, you need to use it twice because it stays on. So you need to switch it to off first and then back on.
If I were you, I would keep the power bank and use a component that gives you (or the TonUINO) full control over the power supply: Pololu als Power-Switch (Einsteiger). With the Pololu power switch (LV), you can activate the TonUINO with a press on the play button, it can automatically turn off when it’s no longer used and you can also turn it off with a long press on play.
Right now the powerbank is still outside the box. It turns on once I connect to the mini USB. I’m wondering if there is a simple solution or if I should just have a USB-C/mini/micro female so that I connect to a power outlet or powerbank?
Are you using a simple on/off Switch and with wich method do you shut down the TonUINO.
In Case you are using the built-iin shutoff timer, the Arduino goes into deep sleep mode, not really fully off. To restart the TonUINO it must be completely disconnected from Power and reconnected.
A Power Bank in Energy save Mode still hast a minimal voltage (App. 2.4 V) at the Output to detect a new connection. This very Low voltage still ist enough, so that the Arduino will not wake Up from deep sleep when full Power ist reconnected.
Thank you! Now I just connect a powerbank to the mini USB and it turns on. When I need to turn it off I remove the powerbank. I’m thinking if the simplest option is to connect a female USB mini/micro/C and just connect directly to either a powerbank or electrical plug. Is this stupid? Or what is the solution that’s commonly used to have it fully portable?
Have a Look at Stromversorgung, there in section 5.
It’s in German but tranlations by deepl.com are mostly acceptable and the Diagramms will Tell the Rest.
Attention: Shown momentary pushbutton in section 5 ist a normally closed type.
My first TonUINO I also powered with a powerbank. Between powerbank and arduino i simply put a latching switch.
You can use some breakout-boards like these:
In my case pressing the switch to on was enough to turn on the powerbank and with that the tonuino.
