I found this article explaining current meter shunts and thought you might find it interesting:
http://sound.westhost.com/articles/meters.htm#s4
If you can find an AC meter in the milliamp range, you could use a shunt to scale it's range to something more appropriate for radios. 1 or 2 amps maybe.
I don't there's any way to make a 10 Amp meter more sensitive though.