The contact width on all of them isn't that wide, maybe < 0.5", but I'm not sure wider is necessarily better. Probably don't want things being too snug either. It's ok if there's a little tolerance (the exposed tip of the CV has a little play, too), so long as it's not wobbling around or creating high/low spots in the sleeve. Main thing is lubrication, but not too much (otherwise the clutch ring won't disengage easily).
Not sure how easy it is to just find a single unit, but if you get a new pair, you'll have at least a spare. Though, seems like these may be ok still. Is there still a gasket in place to keep elements out?