Might consider doing the ATF on top of the 105,000km (minor) service. Was at the dealer today, getting the recall done.
Paid a visit to the parts dept, and they said they had to order in the fluid if I wanted it, service dept also said the same thing.
Also, is this a hard transmission to work with? As I'm trying to decide if I should use the dealer for this, or if I can use my independant mechanic. He changed the transmission fluid on my '07 Toyota Aurion, which he used genuine fluid for (not sure if its the same one for the IS250). I'll definately ask him to order in the fluid from Lexus, assuming their Parts dept. is willing to supply it. Believe it or not, there are some fluids they don't supply such as the differential oil. However I don't think the diff oil has to be genuine fluid, therefore its not a major problem.