He needs to order a sampler and start trying things on. We women have to do that every time we want to buy a stupid T-shirt, and the guys have it easy with their small, medium, and large. Think of it as his turn having to mess with sizes and styles. Start with something labeled "snugger fit," which on the condom sites is always carefully couched as a matter of preference and not brute biological necessity, so it shouldn't be too dispiriting.
Then again, counterintuitive but not out of the question: they're not too big; they're too tight, like a pair of ill-fitting panty hose that can't quite make it past your hips to snug in at your waist, so they keep rolling down, and you have to spend the entire day semisurreptitiously yanking them back up. Not that such a thing would ever happen to me or, I hope, you.
Andrea is home with the kids and going stir-crazy. Write her a letter! Ask her a question! Send her your tedious e-mail forwards! On second thought, don't do that. Just ask her a question.