Dave have you tried looking for the meters from distributors?
The tester do test the circuit under load, and even applies load between L-G. Although it will not test the trip point of the breaker, it will give you the L, N, & G impedances and you can determine the calculated fault current with a little math.
I agree with the crowd here you do not want to test breakers at the far ends unless you can test in the instantanious region. And that region should really be done with engineered manufactured equipment that has UL approval. Sorry about taking you down the home brew road, just the ham radio in me.
