In summer ds wears jersey boxer shorts and a t-shirt to sleep in. (if it's not too dirty he wears the T shirt he's been wearing all day)
Now it's getting colder he could wear his long sleeved t shirts, but what about the bottom half? Is there anywhere you can buy pj bottoms without the top half, or is it cheaper to just buy sets? Or could he wear thin jogging bottoms? or leggings?