There isn’t much translated and online. Pariyatti (if in North America) or the Pali Text Society Websites may be helpful – but possibly expensive unless vitally interested.
Your best bet is to join Dhammastudygroup http://groups.yahoo.com/group/dhammastudygroup/
if you aren’t already a member, and go to their Files section. Click on ‘’ Useful_Posts_2010-12.htm - Useful posts (with links) updated December 2010’’
and read any threads listed under ''K'' on Katavatthu.
Many members of Dhammastudygroup are well-versed in the intricacies of the the Abhidhamma and commentaries, and I find them a very valuable resource.