Anyone know of a schematic for getting 48v phantom power from 9v AC or DC power supply? I couldn't find one but if a usb powered interface can produce phantom power it must be possible.
Sure. It all depends on how desperate you are.
With 9Vac, all you have to do is use a voltage multiplier (google "%^&*croft-Walton) to make a DC voltage above 48V, then series regulate to 48V. Unfortunately, three terminal regulators do not do this because they're generally limited to no more than 35-40V inputs, so you'll have to do some other regulator. Also, phantom power usually has a big inductor in series with the voltage so the signal isn't shorted by the power voltage, so there's that you'll need to provide.
With a DC supply to start with, you will have to chop it to AC in some kind of switching circuit, then either voltage multiply it or use a transformer or inductor to increase the voltage to higher than 48V, and regulate it somehow. There are switching regulators which do this directly with inductors as the up-verter element. Then there's still the inductor to provide.
The process is fairly complex, generally more complex than the thing it's powering if done right. This is probably why you haven't found easy circuits for the application. It's a rare-ish application, and not easily done with jellybean-style low voltage ICs.
In general, any power supply voltage, AC or DC, can be converted to any other power supply voltage as long as enough power is available and you're willing to work hard enough at it and pay for the parts and development.
Frankly, the easiest thing to do is to buy a 48Vdc output power adapter, which do exist.