There's also the Electra wreck in the Misty Fjords area SE of Ketchikan, though revisiting this site would hardly qualify as "an easier way". It could, however, be an excellent source of Plexiglas from the original Electra production line.
I pulled out my photos of the visit from 2004, and there wasn't any plexi apparent. But my photos were mostly promo shots of people.
John Clauss did the photo documentation on that trip. I've called him and he's going to look through his stash of photos to see if there's anything there.
A revisit of this site might be something to keep in mind if indeed there's a test that can distinguish between different plexi formulations.