Interesting - I've never seen that part before. Do you have any additional pictures/details on it?
Doing a quick search I've found the grille online but no luck with the valance.
NEW ABS LOWER FRONT BUMPER COVER GRILLE PRIMED FOR 2013 2014 2015 LEXUS LX570 | eBay
For LEXUS LX570 2012-2015. (Never Been Used or Installed). We will reply within 10 hours you encounter problems. we will within 10 hours, reply back.
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