6v6gt:
You could also look for a variable output buck converter for about $1.
Alternatively, use a 5 volt tolerant ESP breakout and an HC-SR04 rated at 5 volts and a voltage divider on the input pin connected to the SR04.
Your power bank will, incidentally, probably already have step up boost converter from 3.7 to 5 volts, although it is not accessible to you!Mini 3A Voltage Regulator Converter Buck Converter Step Down LM2596/2596S Module | eBay
That buck converter looks too cheap and makes me fell like it will explode 