batteries - What's a simpler way to switch between power sources?

I want to make a device that allows the user to switch between two different power sources (a wall mount and batteries).

I could perform this circuit using two DPDT switches, but I would need to switch the two switches each time I want to change sources. Is there a simpler way to perform this function without using relays?

Here's a schematic of my device as a reference:

Answer

The easiest solution (Initially suggested by @PeterJ) Would be to simply switch only the power connection:

^{simulate this circuit – Schematic created using CircuitLab}

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Alternatively, you can probably get away with just using some schottky diodes:

^{simulate this circuit}

^{_{Wow, Circuitlab is a clumsy tool. It doesn't have entry/exit ports? Or Schottky Diodes? Really?}}

But if you're really loading your RPi or it's USB ports, the drop in the diodes could be large enough that you get brownouts, which would be a real pain in the ass to diagnose.

The best solution, I think, would be to put the diodes before the voltage regulator.
This would mean you would have to have a higher power supply voltage (>7V), but it would solve the problem with the diode V_f described above.