Yes, Fosters Smith carries the Sweetwater - I think you have to get into one of the interior pages of the ordering scheme to see it, but it is there. They look exactly like the same ones that came from the place that Jim mentioned, too.
Mickey asked an earlier question, too, that I missed - you want the AS1, not the others. The thing you're interested in is the inner diameter of your tubing, because the diffuser has a little barb that fits up into the inside of the tubing, not around the outside.
I haven't checked my BP lately. It was way up there in the 150s/120's and the last time was 128/78, which I found to be acceptable. I need to get in for a true doctor's checkup. - I think, in some ways I am fortunate, because I haven't any really BAD health problems (although the high BP was bad enough <G>. My gastrointestinal tract has settled down, I no longer am "loose as a goose." - I find that I'm not as cold as I was - Don't know why that would be - and also I have more energy than I did, so I get more done.