Hi mate. It's the caliper carrier i think your talking about.
You need to get caliper sliding pins, which you can order from Lexus, think they cost about £8 each.
You get two to a caliper, ones the main pin and the other is the sub pin i think you call them.
I'd go back to the place that did/didn't fit your disc's and pad's, it's obvious has hasn't tightened the bottom slide pin.