David - I have a bunch of small VU meters that appear to behave as if they have a logarithmic response built in. I am old enough to remember - but can't for some reason - if I am correct that many VU meters were constructed this way - so that that an otherwise linear signal does not need to be conditioned to get the log (I think that's what's needed) response. If I am correct all you will need to do is procure a VU meter and consider how you might adapt the available input to the range of the meter.
There are a number of ways to take a surplus or discarded meter and determine it's characteristics. You ought to be able to find that via google or in electronics references.