A regular aquarium aerator stone would probably produce finer bubbles than anything you could craft out of PVC.
Plus, now this is just my opinion (others here on the site have heard it before), I don't aerate my minner water. I chill it with ice. Cold minners are less active, need less oxygen and live longer in my experience. And an aerator is just a heat pump. I don't use an aerator in Florida where I now live, and I can keep minners alive for weeks in an iced down (daily), dark Omaha Steaks cooler. You know those thick walled, only Styrofoam ones. Like I said, just my opinion, I'm sure others will chime in with additional advice.