I opened the trunk and the 7443NA bulb is all I could find/reach. The guy in the local parts store claims all lights were working, including the 7443NA which was a turn signal light.
But at night, it is clear that the left top brake(?) light is not.

Top left brake light bulb

(I replaced the top center brake light bulb a few years ago. That was a 7443 (I believe) not 7443NA)

 

All bulbs for 2003 listed here.
https://lightninglab.org/lexus/ls-430/2003/

 

If this is a facelift LS430, the lights that are out are LED's. Only bulbs you'll find are the turn, reverse, and center brake light.

You'll have to either replace with new old stock or find an aftermarket support to fix the dead LEDs

 

I should have mentioned it was a 2005 LS430. I bought the left/driver outer tail light assembly part 81561-50140 for $262 from an out of state Lexus dealer.
See pic:

(The local Lexus dealers in CA wanted about $100 more for that part)
1 hour labor rate to install. It looked easy, but I've had notoriously bad luck working on my car. I'm limiting myself to changing air filters; I even cleaned the MAF sensor once, and replaced the central/upper brake light bulb.

Right before I got the part via mail, the right/passenger inner tail light LEDs started flickering, and went out the day the left tail light was installed. So, a $160 part 81581-50050 on order from the same place...
So maybe these LEDs all start quitting around 17 years. Not too bad of a lifetime, but a little expensive, IMHO.

 

After the part 81581-50050 arrived, the existing light starts to work again!Aren't these electrical problems fun?

 

Probably good that you are replacing them as it is, because if they are doing the "sometimes working, sometimes not" then it's only a matter of time until they don't work at all.

 

Yes, @YoshiMan . It started flickering again. I'll replace it.

Tail light flicker video: 2005 Lexus LS430 tail light flicker

 

I’m not looking forward to the day my 06 taillights start flickering I’ll probably bite the bullet and get brand new ones just so I won’t ever have to mess with them again