So your problem is leverage on VIX? Why don't you trade VIX Futures CFD? Brokers like IG will give you very good leverage. And CFDs are more closely correlated to VIX than ETFs
I use Gain Capital it's pretty good if you use C#
I use Python manly so I have written a Python FIX adaptor for Gain Capital
Called "Transfixed" you can find it on github
