M&S had a lovely looking blazer with a dark navy quilted lining - with the inside pockets- and the essential zipped pockets.
With Thinsulate thermal lining (very smart)
My DS won't wear a jumper (or a coat most of the time) and has no natural fatty padding.
I showed him this blazer , but he curled his lip at it (I knew he would).
But they are out there ,they look very smart.
And if your child is not such a meh as mine...
(I was tempted to buy it for winter but it's excessive to have a warm and 'cool' blazer when he has 2 perfectly lovely M&S soft wool jumpers (virtually unworm)