Yeah, what I need is the valve diaphragm for the 500SE 2nd stage. The only one I've found that contains that valve is this one:
Hollis Service Kit for 500SE 2nd stage
Since this is the reg I have, all the talk about parts for other regs & 1st stages, while interesting, doesn't help my plight.
And,
@W W Meixner - give me a break. You guys act like it requires some sort of combination of rocket science and brain surgery.. In almost all cases it's straightforward, especially if you have the service manual and the tools. The 500SE doesn't even have any special tools. Here's the list: small flat blade screwdriver, 1/4" deep wall socket, 9/16 open end wrench, 13/16"open end wrench, 15/16" open end wrench, wooden dowel, O-ring pick. See anything exotic or complicated to use? Nope, didn't think so. In fact the part I need to replace is a simple unscrew, drop out the part, drop in the new part, screw it back together - done.