http://www.mygranturismo.net/gear.php?id=21059&compact=
Shows a picture of at least one of every type of helmet. Spinning ball and gravity helmets would be you best bet, not exact matches but similar. In terms of colour I will have to look through them to see if any match the colour of Senna's helmets.
*Edit
None of the spinning ball helmets match exactly, the closest I can find is either spinning ball 11, or spinning ball 23
I gave my A.Senna Bob BackVision 23. No blue stripe and one red stripe too much. But best there is, if you use a red suit, the red in the helmet looks ok and you have mainly yellow with a green stripe. Best option!👍
