The kids and I have really been enjoying the 1:32 cars on a 1:24 track but it does take quite a bit of space.
I used
www.carreraslots.com with great customer support. They have 1:43 cars and track in stock, but it looks like they are sold out of their complete sets.
Hmmm, I wonder how the 1:43 cars run on the 1:24 track?