Ron,
Try:
1877WeRbolts.com - Standard and custom bolts, nuts, washers, machined parts & blueprint fasteners in stainless steel, English and Metric Chicago Industrial Fasteners 1877WeRbolts.com
I have found them to be a pretty good high end hardware source. CAV also had a kit to replace the wrong upright hardware pieces and that is what I used on my car. But that would have been in the pre-Autofutura era and I don't know if it is still available. (Roy Sales may still have some). The new post-100 CAV upright apparently won't retrofit.
As far as hardware goes, for those of you that like to scavange, go to military (preferably Air Force or Naval Air Station) base property disposal yards and you can find all sorts of high grade AN and milspec hardware and fittings often for pennies on the dollar. All of the control yokes, fittings and connections for my race car are milspec and some of the aircraft parts have quite the trick look about them. Helicopters in particular are great parts sources.
As far as the CAV upright problems go, my understanding was that there was an error on some of the early cars and the upright block bolts used were not only the incorrect alloy grade but were also too short. Both issues certainly are cause enough for a problem. When I put the kit on my car, it was clear the bolts were not only higher grade but also much longer. The mixup may have been related to the very early MONO cars being farmed out for assembly.
I am not aware of that many GTD/CAV upright failures given the numbers out there so I'd be more immediately concerned about bad hardware than a flawed design. Cliff's solution certainly would add piece of mind though if you plan on banging curbs on trackday. But everyone should immediately verify the hardware is correct if they have not done so.
It would also be interesting to see if ERA, sprint car or other sports racer uprights would fit.