Disclaimer : I don't own any Campagnolo SR Pedals
My understanding is that campy used an oversized spindle (because Ti is 2/3 the weight and 2/3 the strength of steel.) So, the cups would need to somehow be larger, or at least a different size, so that the ball bearings would fit perfectly.
Thankfully, Peter brueggemann just posted a link to a guy / shop in hungary with lots of NOS campy parts. In some of the pictures I saw NR or SR spindles.
There's also http://www.campyoldy.com and http://www.universalcyclecentre.co.uk and mercian cycles in the UK as places to look for spindles.
If you have an NR spindle, which is presumably smaller, then can't you just use the next-size larger ball bearing, in the appropriate size (do some experimentation to find out what works?) I don't think it would shorten the life of your pedals. Take any NR pedal and experiment with moving the spindle around.
Do you really want a Ti spindle, anyway? Do you really want to break that pedal again ??
- Don Gillies
San Diego, CA