Update: Sam actually likes his sweater. Or, at least, it chills him out. He’s an anxious cat and gets really anxious when we have a lot of company over (as one does when it’s holiday season).
He has a “thunder shirt” that chills him out substantially but it’s been misplaced. Meg knitted this for fun a while back and we found that Sam will happily wear it pretty much all day. He’s also very good at slithering out of it when he feels like it.