Dear all,
I found the following supplier of new auto-wiper "Gel Pads" and reconditioned auto-wiper sensors.
This link is for the RX specific gel pad, but the eBay seller "Rejel" stocks parts for Lexus/Toyota and many other makes.
http://www.ebay.co.uk/itm/RAIN-LIGHT-SENSOR-SILICONE-PAD-FOR-LEXUS-GS-IS-LS-RX-MODELS-/110992303219?pt=LH_DefaultDomain_3&hash=item19d7a82473
I hope this is useful to someone!
Chris.