maybe your not looking at the right place..... try this
http://modelsport.co.uk/?CallFunctio...=1#SeeProducts
now from what it seem al the 40 series wheels are roughly half offset prolly due to how wide the tires are... so take your pic from that page
here is a 17mm hex
http://modelsport.co.uk/?CallFunctio...n&ItemID=27852
the rest are 23 mm hex and they all say so in the title.