Yes, There are PSU's Avilable ranging from 120 Watts Output reffered as PICO psu's, But avilability in India Is a Issue, You may instead use a Dc to Dc Converter used for Car PC's, but the setup could be expensive as you will have to buy a battery, charger to charge the same and a converter.
you may go for alternate configuration if you are looking for power saving and are ready to sacrifice portability.