I have two alternative suggestions for an 0.0066666 Ω current sense resistor.
You could use three of these
0.02 Ω current sense resistors in parallel. As Jim points out, you need a big bit of copper or brass to connect them to, so the there is little effect from any additional connection resistance.
Or you could use one of these:
0.01 Ω 4-terminal current sense resistor. That is a 4-terminal resistor, so like the shunt pictured in this thread, it has current terminals and sense terminals. Now i realise that you can't get 0.006666 Ω, but that can be worked round. 0.1 Ω is 1.5 times too large, so if you increase the resistance of your meter by 50%, it will work fine. If you measure the resistance of the meter, or it might be written on it, and just find a resistor of half that value to put in series with the meter.
(There is a 4-terminal resistor in that range that is 0.008 Ω, which would be closer to what you want. You would need a resistor that is 20% of the resistance of the meter. However, 0.01 Ω is a lot more common, and Newark have that in stock)