Look for the G508 rebuild kit.. they are $30 on ebay and include all the parts. Since they are milsurp they include all the parts. I rebuilt mine and got the check disk out with a drywall screw.
http://www.tm9-801.com/forums/viewtopic.php?f=1&t=468You will need to log in to see pictures. Its not a true step by step, but I do talk about the check valve.
