Dreamcast SD Card Activity LED?

I've just hooked up an SD card reader to the serial port using the schematic below (apart from the LED), but was wondering if it would be possible to have the activity LED constantly on as standard and flicker when it's being used? Reason being is that I would like to hook up a 5mm blue LED and use it to replace the power LED, instead of having two separate LEDs on the system.

 

Easy. Use a PNP transistor. Wire the base to the access LED point and the emitter to power and the collector to the LED.