In short, you can use any USB Audio Class-compliant hardware interface with your iPhone.
Since you are using a B&K 2807 power supply, you'll want to make sure that you choose an audio interface that supports the range of voltages that your 2807 will produce with your chosen microphone and the acoustic pressure you expect to measure. The 2807 can output up to 30V, which can be difficult to find in an audio interface, but which you also may not need.
You might want to consider USB Audio options available from MOTU, RME, and CEntrance.
If your B&K microphone preamp were a CCLD-type, then you would't need a separate power supply and could use the 485B39 from The Modal Shop. The 485B39 would be a very portable solution.
