Long torso short legs

So my son has a short legs he can still fit in like 12-18m pants or shorts and his waist is so small that 2T pants just fall down with no pull strings but his torso is so long 2T shirts don’t fit anymore like his belly hangs out from all shops target Carter’s old navy and children’s so he needs 3t now so my Dilemma is for pjs 2t pants stay on as well as I can hope but I know 3t won’t so does anywhere sell just pj shirts or are they too young? I know I can just put him in regular shirts but then I’m waist pj shirts