switch mode buck converter is the only solution at these current loads. you might use current mode chips like UC3842 supported by power MosFET of proper wattage. as the wattage is well above 600 including system efficiencies, proper care is to be taken in component selection and placements.
If you think the load can work with 24Vdc then there are planty of devices that covert 48Vdc to 24Vdc ..
Here is one example: E756 10A 48v-24v Voltage Converter
I have fonud some. See this one. May be it will helpful for you.
PKL 4316 ,MV48-28-600, FNW500-700 Series etc.
see this link for datasheet of FNW500-700 Series **broken link removed**