I have a Rode Video Mic Pro that I constantly need to change the battery on. I often use it as part of a rig- so 5v USB power is readily available.
The screws are aligned so they securely make contact on the inside and line up excellently for the 9v battery profile.
The step up converters come with instructions. I just followed them (turning the adjustment screw) and TESTED THE OUTPUT VOLTAGE!
I found the converter on Amazon here:
Icstation MT3608 Mico USB DC Voltage Regulator Step up Converter
All USB cable ends I've seen are too long to fit completely inside the housing. Having the cable come right out of the bottom doesn't suit too many scenarios anyhow. I'm handy with a soldering iron, so I eventually made one where I snipped off a cable end and attach it directly to the soldering pads on the board. Then I drilled a hole where I needed the cable to come out.
Although a cover isn't needed- I created one just to cap things off.