I tried to find something suitable today in a specialist tool store, they looked at me like I had two heads when I described it...
As Craig said, the actual socket part of it needs to have a really thin wall. The Losi kit wheels probably would be OK but the ones I use for foam are impossible to get a normal sized socket into as the recesses are deeper and narrower.
It's a pain in the neck as I just bought the low profile wheelnuts and I'm damaging them every time I change wheels.
Fingers crossed, I can get hold of something suitable soon...real, REAL soon