Endless googling and ebay-ing must surely unearth something in the U.K.?
Don't try to outsmart the designers. This is not the Auris. It's your car so you can do as you wish but it's not a good idea.Drivetrain should be able to take it, with Auris hybrid towing is allowed but max trailer weight is only 350 kg. Lexus is offering a bike rack which requires a tow bar installed, it could be made by Brink I think. Atleast the coupling is Brink/Thule -style..