Lexus do indeed still sell the TRD skirt, think it's about £170 odds unpainted? So you'll have to cough up for it to be painted and fitted (unless you're confident about having a go yourself)
PM ACLex about it, he works in Lexus parts, and has posted somewhere on here (need to use search as I can't remember where, maybe his January Sale thread) a list of the TRD Part numbers, and prices etc