If the final device is to be battery powered then @microMerlin 's suggestion of a mosfet driver is a good one. A mosfet (it needs to have a logic level gate so a 5V micro can drive it) connected to the ground side of a string of 4 leds (or less if they are not red) both removes the current limitations and improves efficiency (i.e. battery life) as less power is wasted in the current limiting resistor.
Peter