I think I might be the only person that has those. I had to order a special run from CTS, because they didn't exist. They weren't cheap either, it was like $20-$25 a part if I recall. I'd have to find the box, though. It got packed somewhere when we moved.
Word of caution, using a blend will interact with your pickup volumes, if you have them. It's not a problem if you keep your volumes on 10, but if you are mixing levels, then trying to use a blend pot, you can get a weird volume drop or warble as you turn the blend and the resistances add up. It'd be better to have a blend and a master volume, or just the blend and no volumes on the guitar.