Since we are pretty sure it's power supply noise, a good quality USB Audio Interface that's not USB powered should be an improvement.I almost feel like forgetting the mic and going with an XLR to USB converter, but if it's the system...
You could try buying a regulated "linear" power supply to replace the one that came with the hub. A linear power supply isn't necessarily quieter than a switching supply. It's possible to build a good power supply either way.... A switching supply is more efficient (it doesn't get as hot and it doesn't waste as much power), and its typically smaller.
If you get noise from a from a linear supply it's usually 50/60Hz power line hum. Nose from a switching supply tends to be higher-frequency noise with lots of different frequency components (more like "whine"). I assuming the power supply that came with the hub is a switching design, since you're still getting that "switching noise".
I was searching online to see if I could find a USB power filter.... I found this, but it's priced for "audiophiles" (It cost's more than the microphone) and I have no idea if it works.