Accurate -2V reference
This answer was given before the OP kindly changed the requirements from +2 volts to - 2 volts therefore it's still under construction

Use the 2.048 volt reference and a potential divider after the 2.048 volt output to produce precisely 2V. Then using an inverting configuration op-amp running from negative and positive rails invert the 2V to -2V - possible op-amp choice is the AD8657







simulate this circuit &ndash; Schematic created using CircuitLab