RX400h rear suspension bolt sizes

[TouringRob]

Hi there, 

I will be replacing the rear front/rear ball joints this week. After having a look earlier in the year I was unable to remove one of the bolts as it has seized into the joint which just span. Looks like I will either press the bolt out or cut it, either was it will likely be damaged. Does anyone know what size they are so I can order non Lexus replacements? would imagine they are 10.9 or possibly 12.9 in grade. 

Seem to be Lexus/Toyota part number: 90080-11672 which are not easily available in the UK other than via dealer - feels wrong paying £50 for nuts and bolts! 

Any help would be appreciated, I've bought Febest joints and a press kit so hoping to do the job without removing the hub assembly. Persistent knock from rear end not cured by replacing anti roll bar links or bushes, would be happy to posy pictures of the process should anyone wish to do the same! This is a 2008 400h with just over 100k so I would expect many owners will be facing similar noises by now, Lexus will only sell the complete hub. 

Many thanks 

Rob