Same deal here, rears are there but no front.
But guess what, found out that overseas they do have OEM Mudflaps to suit the RX330/RX350. If you're interested, the part number is #08414-48820.
Couple of places on ebay sell them :
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=110573056580&viewitem=&sspagename=STRK%3AMEWAX%3AIT
http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=370416909098&ssPageName=STRK:MEWAX:IT
Also found them on some of the lexus dealer sites in the USA. I like the OEM fitment on them, they look quite nice, I'll put in an order in a couple of weeks so will report back on them.