Diaphragms are really hard to find lately.
I think they are revamping the design or something.
Just FYI - take it for what it's worth and YMMV, and assume your own risk - but you can order them from reputable overseas pharmacies. They have all the sizes available, and there actually is an "Average" size.
When we did not have insurance, I paid $150+ to get fitted, and then to order one, and then spent 2 weeks trying to find one, only to realize after the first few uses, the doctor had gotten me one that was WAAAAAY too tight.
Which brings me to another point - trying to find an office to fit me for one was nearly impossible. B/c hardly anyone uses them, every place I called was like, "I don't even think we do that here" or "Um, you have to be fitted for those? Let me check if we can do that."
when you do get fitted, make sure you get up and WALK AROUND with the diaphragm fitting thing IN. This is important b/c when you stand up, your organs put pressure on your pelvis and if the diaphragm is too tight, it will be painful to wear for the needed time. It should be comfortable enough that you don't feel it there, but snug enough to stay in place.
I ordered one from an online pharmacy for $20 in the next size bigger (Which was the average size that most women are) and that INCLUDED shipping.
Anyway, just an FYI,. Things may have changed since I got mine a couple years ago. And it could also be the area I am in, too.