The actuator is built into the whole assembly. It is not serviced separately. Do not succumb to the temptation of buying the supercheap part that you have to modify the door in order to make work. This will only make life more difficult for you. In my professional opinion by the part $100 cheaper than the dealer at wholesale prices as you mentioned above and install it.
You could try www.MetroToyotapartsnow.com they may be able to give you access to Lexus parts at good prices send them an e-mail see what they say.