Depending on how much money you want to spend for me you can't beat the Hayabusa pro insteps.
http://www.mmawarehouse.com/Hayabusa...efault,pd.html
I use these personally.
If you don't want to drop that much the combat sports one are very good as well, just not as well padded.
http://www.mmawarehouse.com/Combat-S...id=shin-guards