Zipp o ring sizing?!

I need to replace the o-ring 'bearing shields' in my Zipp 'v9' 88/188 hubs, and Zipp doesn't even list a part number for the rear o-ring - in some of the manuals they even forget the V9 rear hub has larger bearings than the V7/V8 ones!
Does anybody know what the specification of these o-rings is so I can just buy them from the bearing supplier? I'm guessing nitrile rubber, look like a 1mm section and I get them with an OD 1mm smaller than the housing diameter? I forgot the measure the housing bore - would need to take the hub apart again to measure that!