I can't seem to find any and I have had them in the past from places like JL, Vertbaudet. Basically a short-sleeved or sleeveless knitted cardigan which can be worn over a roll neck or long sleeved tee. They are so useful for the cold months as my DDs (5 and 8) don't like being encumbered in two layers of long sleeves but like having a warm 'chest'/middle.
Any ideas gratefully received!