Ah yes, the slide diaphragms were ordered from Sirius Consolidated, a Canadian company recommended by someone in my CB350 thread.
They were a great replacement, though quite tricky to install. Here is a CB350 slide diaphragm replacement trick (ok, four):
* The diaphragms can be physically pulled from the slide; you have to be gentle but firm. Be careful not to tear the diaphragm, even when removing. You don't want to leave rubber bits behind.
* When installing new diaphragms on the slide, take some grease on the edge of a piece of paper and run it all around the inside of the slide's lip where the diaphragm seats. You will have a hell of a time getting the diaphragms seated without that grease.
* You can start the seating process by pulling he side on the opposite side to essentially "suck" the inner circumference into the lip. Don't over do this, though, as it can make distributing the rest of the circumference difficult (bunches up).
* It will be virtually impossible to get the entire circumference of the diaphragm to seat just by pulling and pushing. Be very careful about how you push in the diaphragm. I found the best tool was a Bic pen cap. I used the pointy part (the leftmost point in this image), to very gently push it in.