I had this problem with my PX-10. @
bulgie advised me to shorten the head tube, and I also didn't want to do it. My problem was compounded by the fact that I wanted to get a brake hanger in there. I ended up finding an unbranded French headset on eBay that had a shorter stack height.
A few pics...
The "problem" headset:
The lower cup was also bigger than it really needed to be:
Various toothed washer and hanger combinations I found:
The shorter headset:
The shorter headset fully installed:
Note the lower headset cup compared to the problematic one above. If it helps, you can mix and match top and bottom cups, and I think you can even use a non-French lower cup as long as it's properly matched with the crown race.