good luck. i looked for a while online for the new gmc 20" rims. i never did find anything close to la. they had a few sets on ebay for around 850 - 1100 with decent shipping prices. this was all around 6-10 months ago though. i kind of gave up on them and decided to just save my money for a gmc with that already has the 20's on it.
ps. - you ever ride in the lafayette area?
check in the for sale section on gmfullsize.com too. i had seen some sets on there also