I broke mine recently, and I'm pretty sure it was more that £25 new for the whole thing from Lexus. Hopefully Stav is right, but when I was looking for mine I'm sure I found a post saying it was £100 plus, see below
http://www.lexusownersclub.co.uk/forum/ind...1&hl=aerial
I got a replacement from the States, see eBay # 300312019524
Just checked for you, they have another two up for "buy it now" or offer
See # 360159949048. I got mine for $65, plus $23 for postage, but I reckon a lower offer might win it too.
Good Luck