Google the item that you want and you should see used Lexus parts dealers, after market replacement parts dealers, ebay sellers, etc..
I got mine for same color used for about $100 to $125. Yes, I changed a few times already. My body mechanic charged me $60 to remove and replace the mirror. When you buy the mirror, check on the overall condition of the mirror. Get a digital picture if you can. Make sure the hinge part is not loose, otherwise it will vibrate while idling.