Pad carriers are the brackets which attach to the hub and hold the pads in place. The caliper also attached to the carrier using slider pins and bolts to allow side to side movement of the caliper.
Picture below shows the pad bracket on the left and a slider pin on the right.
Normally brake problems arise due to lack of lubrication on the slider pins which causes them to seize in the holes on the bracket resulting in poor braking performance, the pins can generally be freed up with a good dose of WD40 then cleaned,regressed and refitted but if rusted or severely pitted they need replacing.
Cannot quite understand why you need new pad carrier brackets unless the slider pins have completely seized, the brake pads themselves sit on stainless steel inserts fitted into the carrier brackets which do become clogged with brake dust but easily cleaned up.
The calipers rarely need replacing providing that the piston is free to move,there are no leaks from the piston and the seals are intact, I did the rear brakes on a fellow member’s lS400 recently and just the pads and discs were required.A couple of slider pins were tight but soon loosened up and were deemed serviceable.