I intend to swap my indicator bulbs to LED ones, and I read that would cause the lights to blink real quick 'cos of the lower wattage.

I also read that instead of mucking around with resistors, cutting wires and soldering, I can replace the indicator flasher relay with one compatible with LEDs?

Anyone has experience with this? Know where to get one from and/or know where the flasher relay is on the Altezza?

Also read if you swap the flasher relay, then the indicator lights don't flash when you turn the alarm on/off 'cos the ignition is off, is this true?

You could always just wire the LED's in parallel with the original lamp tucked away somewhere. LED's draw very little current so it wont overload the stock circuit with the original lamp connected.

Otherwise measure the resistance of the stock lamp and find a 10W Resistor with the same resistance and wire it in parallel with the LED lamp

You can buy the flasher unit for the Lexus/altezza off ebay

Does anyone know where the flasher relay is located?

I've listened to the clicking sound, and located it to be somewhere near the drivers side fuse box, but not sure of the exact location:

bump, anyone knows where the flasher unit is on the car?

Should be a chart on the back of the cover that you took off to get to the Fuses.

It's located on the inner driver kick panel circuit.

That's what I gathered, hence the picture of the driver kick panel above, but I don't see anything that looks like a relay, all of them seem to be plugs and fuses.

If someone can circle it or something it'll be helpful.

It's on the inner circuit. Which means it on the other side of the fuse board (the board in your photo). Viewing the circuit board from the back it's located on the bottom left.