I didn't just use "led bulbs" i actually soldered together a few 5mm LED's. I tried simple LED bulbs but they didn't distribute the light. There were hot-spots, it just looked terrible. With soldering a few 5mm's together, i could angle them every which way to get the light where i wanted it to go.
There are different size bulbs in each portion, one type for gear shifter area, for heated seat buttons (really tiny!) radio buttons too. You'll have to take it all apart and take inventory, i don't remember exactly what types and how many there were.
To get the console apart, put the car in "ACC" and put the shifter to "N" to make room. Remove the wood "U" that's attached to the trim around the shifter area. Get a small flat head screwdriver and gently pry it up from the bottom of the "U". Then you'll see two screws on each side of the console. When you have those out, YANK as hard as you can to get it out. There are just clips holding it in from there. Turn the car off, unplug everything and start taking the back of the radio apart. You'll need to take EVERYTHING apart, and i mean everything. The bulbs aren't visible until you take it apart... They're really small too. Not sure if LED bulbs would even fit in there!
My rx300 has navi, not sure if yours does. It may be different back there.
If your rx has the heated seats, you need to take the switches apart to access the bulbs. Again, REALLY tiny. I don't think they make LED bulbs that small, they're basically the size of a 5mm LED. The cig lighter bulb is easy, along with the shifter lights as soon as you get it apart.
I think this modification hasn't been seen before because of the level of difficulty. My guess is people just get scared when they take the cluster apart and aren't able to see bulbs.
If you're determined, and have a lot of patience and a little soldering ability you can do it. Took me about a day with my son to do this. and i'm currently having problems with the LED's flickering- evidently the voltage going to these bulbs has a slight fluctuation which the LED's pick up.