I think the "swirlies" usually get chopped out of the US versions of Rocco's films, so be sure to get the Euro versions, where possible.
I haven't seen any of these, but have read that there are toilet-bowl scenes in...
Rocco More Than Ever 2
Rocco's Animal Trainer 5
Rocco's True Anal Stories 4
Sandy Insatiable
...and I believe in "Dirty Anal Kelly in Rome 2", Kelly gives one to a man, after beating him up.
Check out as many reviews of Rocco's films as you can -- particularly the Animal Trainer series. There are probably more scenes than the ones I've listed. There's also a possibility of a toilet-bowl scene in one of the "Prague" series.
And yes, as pornpope said, from the U.S. there's "Swirlies" and "Swirlies 2" by JM Productions.