Part market for Lexus GS 450h & IS 250

Hello, a well-known one of me would like to get a Lexus, since he has always done everything on the car for himself the question arises for him what it looks like with the parts supply e.g. in the internet? Have looked around me and it looks very rough in comparison to share it for German manufacturers, if you want to order parts to then install them yourself. Alternatively: Can you get all possible replacement / wear parts at Toyota? If yes how does it look there with the prices? Beisp iele for GS 450h & IS 250 would be good! Thank you already in advance for your help!