Me again,
actually there is an appropriate band available.
The near_infrared (B5) can be used.
The problem is that the user can select if the values in the product shall be shown as radiances or reflectances. So, fixed values cannot be given here.
By default the values are radiances. In this case you can use this expression:
near_infrared > 0 && near_infrared < 25.
If you have switched to reflectances, the same values as for S2 should work.
near_infrared > 0 && near_infrared < 0.1
Maybe you need to change the values a bit.