I've been spoiled rotten having Precision Integrating Sound Level Meters, whose analog meter have at least 25dB range, often 30dB or 50dB with linear dB graduations. Basically TRUE RMS converters driving Log Converters to yield fast response, variable damping, and produce a much wider range than the traditional Analog VU meter as you're considering. Also Measuring Amplifiers with meter circuits offering 50dB Log range, 20dB Linear range (with VU-like scales), plus offering Peak Reading.
Now, in the used signal processing market, you'll find compressor/limiters which have meters with often wider range than a common VU meter, done with LED indicators....GRN for the -30dB thru -10dB range, YEL for -8dB thru 0dB, and RED for the range above, which may go 10dB above '0VU. There is an IC that National Semiconductor made (LM3915) having a 30dB range, in 3dB steps that many companies have made use of. Some gear will also have Peak indicators besides the VU meter indicators. You might find some old dBX gear or similar with useful meters (all would normally be 1 or 2 rack units tall, 19" wide panels. Finding something that needs repair could be a place to start, depending on your expertise in electronics repair.
There are no doubt VU Meter kits out there if you search long enough. I haven't looked. I had picked up a Tektronix 760A L/R & L+R linear LED meters that give both VU and Peak reading simultaneous, as well as having an XY scope display of the waveform (waveform monitor for use in broadcasting)....I think I had paid maybe $150 for it. Overkill for your needs, but, there are many options out there for metering. I personally like seeing a wider dB range than the limited range an Analog VU meter yields. That's just me, of course.
You might post some ebay links to the particular items you're considering so we can have a look and comment on further, depending on how much info the seller is providing. At any rate, a worthy project, with many ways to go. Lots of used stuff out there that could be cannibalized and adopted for the task.
There may be old retired Teac or similar tape recorder electronics having usable meters with their meter circuits that could be hacked and repackaged into your small box.