The bolts on my headset have rusted. I'd like to replace them. Is there a standard size, or do I have to match them individually at a hardware store? (Cane Creek)

I think you mean stem bolts.
They will be metric. Not all manufacturers use the same size.
A good hardware store will be able to supply some.

4mm M4 bolts are pretty commonly used in stems, however, some manufacturers differ. Just go to any decent hardware store (bring one of the old bolts) and ask them to point you towards the stainless steel metric machine screw section (doesn't have to be stainless, but after you get stainless, no need to worry about rust). Some of the stems use custom bolts, but most of those customizations are merely cosmetic. As long as the bolt head is the same diameter, it should work perfectly in place of the originals. Sometimes the customizations are to narrow the bolt head to make it fit in a recess; if you can't find a bolt to fit in the hardware store, you can use a power drill and a file to turn down the head diameter of the hardware store bolt down to the right diameter.

Or you can go to your bike shop and pay $5 for a bolt you'd get at the hardware store for $1.25. They sometimes can get the replacement bolts.

Lastly, rarely is the rust on stem bolts more than cosmetic. Most of the time if you take them out and spray them down with WD40, most of the rust will go away and they'll look okay again. Then, once it's clean, you can coat the bolt in a thin layer of machine oil to keep it from rusting again.

my local pep-boys auto parts store has a section of metric stainless bolts, i actually just replaced the one that holds my stem cap on, that one was constantly rusting, because its right up top and holds sweat, grime and rain. stainless is the way to go.

I was told at an LBS that stainless and titanium bolts are bad, mostly due to the high stress location they are typically in on a bike (stem bolts, handlebar bolts, etc). Why would they think this?

A titanium bolt on the stem might be a bit more prone to break if you over torqued it. But you don't need that much torque to get it to hold in the first place (and you don't want to crush your carbon steerer anyway) So I'd say they're full of it.

I use Ti bolts in most of my stems for cosmetic reasons just because I live in a coastal environment prone to rust and haven't had any problems.

Thanks all for making this one of the rare useful-info posts on the 41!