ip,

Please provide more detail of your system's valving setup. How many valves total? Are they configured in parallel via a manifold system? How old are they? With what type of pipe material is your system installed? What is your systems static pressure? Aloha

Here some sites that could shed some light on obtaining repair materials:

http://sprinklertalk.com/wbb/index.php?page=Thread&threadID=1271

http://www.basicirrigation.com/toro-hardie-richdel-rainjet.htm

http://www.wateright.com/index.asp?PageAction=VIEWCATS&Category=21