Cheap 500mV reference
what about this 
http://www.analog.com/static/imported-files/Data_Sheets/ADR130.pdf
cheap from digikey circa $2 for single units, wide input voltage range (2-18 V) stable output over temperature a wide temperature range of 50 ppm per degree C, and +/- 0.7% initial accuracy, and small size TSOT package.

Use a voltage divider on the input side to drop your 4.8 V - 25 V to 2.4 to 12.5V which is suitable.

I think that is a tick in every box :)