Chuck,
Didn't want to open up the gun again and have it laying around until parts showed up, as such, I wasn't sure of the exact ID of my Whisper at the time, so I ordered this two seal kit from Maccari.
http://www.airrifleheadquarters.com/catalog/item/251485/5499150.htmWhen I finally got the gun apart,the smaller diameter of the two seals in the kit was closer to the OD of the original seal so that's what I used.
I also ordered Maccari's lube kit to lube the new seal with, and have the other lubes included just incase I ever put the spring back in.
http://www.airrifleheadquarters.com/catalog/item/251484/4169286.htmAs for a spring, he has them also, but having an air venturi already in the gun, plus the original spring as a back-up, I didn't order one so can't help ya there.
Paul.