My great friend in Arizona makes something that just might help you...and I believe he will ship it out...and give instruction for a fee....much cheaper than conversion.
Here is his website..his name is Bill...please tell him Tony Neumann in Colorado sent you....
good luck
http://www.members.cox.net/tismaz/billtism.htm
Sprinkler Solutions, Inc.
Arizona and Colorado
www.sprinklersolutions.net