ebay, ebay, ebay

A few months ago i scored a new set of Rx400h wheels chromed WITH tires, for $1300 shipped. I wanted the OEM wheels just chromed, to keep the hybrid style.
I did the same thing with my old Rx300, found someone on ebay selling the factory wheels chromed for $600.
If you like the factory design, check out ebay for sure. There are a lot of companies on ebay from CA that strip the factory wheels and tripple chrome them.
At first i was hesitant because i didn't know if the chrome would last, but i put 3 years on the chrome set with the Rx300 and am pushing 2 months on the Rx00h wheels. No signs of pitting or peeling whatsoever.
The key is washing them weekly and keeping them away from snow and salt. Being in Rhode Island, i have a factory silver set i use in winter months and switch to the chrome set during summer. Since you're in AZ, you should be fine year round.
They also offer an "exchange" where you send in your factory set, pay $500 and they give you a chrome set. Might work for you since you don't need a factory silver set being down south.
http://cgi.ebay.com/ebaymotors/LEXUS-GS430...sQ5fAccessoriesgood luck!