It looks like the worst-case accuracy over temperature of the INA209 is +/-1%, so together with a 1% resistor should get you a tolerance of 2% worst-case. If you're only going to use it at room temperature the INA209 says it is +/-0.5% accurate so together with a 0.5% resistor will get you the 1% specification.
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The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, speaker, microphone, light sensor, potentiometer, pushbuttons