Halfords didn't have any when I looked, so I bought them from Lexus. Seems strange that the ones that Lexus supply tell you to consult your dealer for fitting instructions. Maybe they have an 'arrangement' with Lucas or something...

All that is visible on the light itself is 2 little circles, so I didn't fancy making a guess. I will be certain to ask them for a quote next time before getting small jobs done.
Anyway, I know how to fit them now. If anyone else wants any fitted, I'll do them for £20, and If they are LOC members, I'll even knock the VAT off. That's less than half of the Lexus main dealer price. Bargain.