One fine day, the /6 in my 65 Valiant stopped idling, but would run great as long as I pushed the gas pedal. I had a look under the hood and found that the fast/regular idle cam piece on my Carter BBS had fallen off, along with the screw that attaches it to the carb. Unfortunately, the parts fell onto the road somewhere.

Do they happen to include these parts in the rebuild kits, or are they otherwise available new someplace? Do I need to find a junkyard carb to take them from?

I don´t know, but maybe other carters used the same parts?

No, those parts aren't in any carb kit. You'll have to rob 'em off another carb. There were a few variations on the fast-idle cams in Carter BBS carbs over the years, but any '61 or later cam from an automatic-choke BBS will work OK, and the retainer screws are all the same.