I recently bought a cheap VU meter on Amazon, which looks very cool but needs some circuitry to get running. Unlike vintage meters, which can be driven by the audio signal directly, newer (and especially cheap) meters require DC current. A simple circuit, based on this example by Rod Elliott, uses four diodes to convert the AC audio signal into DC, plus a resistor and capacitor to dampen the movement of the needle.
See Rod’s post for lots more technical detail and a more complex driver circuit. Of course, this is pretty lo-fi and not studio-quality equipment… it also didn’t cost $1000.