I also found this unbalanced 1.5m XLR to 3.5mm cable for a decent price:
Smarter Shopping, Better Living! Aliexpress.com
www.aliexpress.com
Look what it says:
"This is the Unbalanced cable, which combines the left and right stereo to the mono input, the L/R channels that soldered together, making the mono signal to XLR Pin 2, the XLR Pin 1 and Pin 3 which shorted to ground, not the balanced cable"
and for the same price and length theres this 3.5 to TSL cable:
Smarter Shopping, Better Living! Aliexpress.com
www.aliexpress.com
I don't think you can connect your Google device to those speakers directly.
The first issue is the DC offset of headphone portable devices. They have a few mv of DC offset, which drops when a headphone is connected, which is low impedance. So this drops the DC offset and is used by the device to detect that headphones are connected.
Now I don't know what the signal output of your Google device is, but it is likely the Android standard, which is 150 mv. That will not be nearly enough to drive your speakers, which will require a line voltage of 2.3 volts, if it follows conventional practice. There is no proper spec. for those speakers, which look optimistic to say the least. I don't care how many 2" speakers it has, but it will be pretty much useless as a PA device. It has eight 2" speakers crossed at 260 Hz, where there is still lots of power and a requirement for more cone excursion than 2" drivers will have. So for a start you have fallen victim to a pretty significant con.
So I do not know what will happen to your device if you common the output. It could be bad, and it also could be risky to send DC offset to a high impedance input, as DC could be present at the output then. Many amps will amplify DC these days.
As far as going from unbalanced from your Pixel device, that is the easy part, as you would need a 3.5 mm to a mono phone jack, and when you connect that to a TRS female connected it gives you an unbalanced signal. However that will connect the outputs of your pixel together and that could be risky, de to the DC offset issue.
I think if you must pursue this, then you need a mixer to interpose between your pixel device and you speaker.