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Any Lexus GS, IS, ES wheel will work. Avoid the LS as its a different lug pattern.
As far as tires, use a https://tiresize.com/calculator/ tire calculator to match the new size tire to your old ones. Only the height of the tire matters for the AWD system, and you have about 5-10% allowable difference to avoid a warning light. So you can run 17-20" wheel aslong as the tire height matches. Should be able to find many on craigslist or ebay.