I've had some luck with Ammoseek.com and bought 2 cases of Rio shells for skeet, $104 per case shipped. Which is better than Cabela's could do and I got a load I wanted as opposed to whatever Cabela's had available (if any)

It seems the Italian and/or French ammo makers are getting caught up and their ammo is making it to the U.S.

South Georgia Outdoors is a legitimate seller

Ignore any vendor that doesn't accept credit cards
If it seems too good to be true, it probably is