Instead of drilling, I used a stubby awl to poke a small pilot hole at each dimple in the lip. It worked perfectly and there was no need to remove the wheels if you have a stubby or 90 degree screwdriver.
They're $80 for OEMs from Prestige Lexus. Pretty simple to install yourself.

 

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I just installed ours in very little time without removing the wheels too.

PK38913P00TP $ 73.00 Mudguards, Black





It has rained the last two days and she's dirty.









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I purchased two sets from Amazon for both my RX and NX models. Both are excellent quality, despite being aftermarket. They were both a breeze to install and look and function as nicely as the OEM product from Lexus for about half of the Lexus cost.