Well, if any of my fellow Canadians are morbidly curious, I discovered by testing against an opened display sample at the local Chapters store that a Moleskine KoboTouch cover (the one that comes with the notepad) will just barely fit the Sony PRS-T1 rather tightly, but with no overhanging/sticking out bits once you've gotten it slotted in correctly and you can even press the power button through the covering holding-strip at the bottom. Access hole at the bottom doesn't quite match up with the USB and just barely clears the earphone jack, IIRC.
It's a very tight fit, and even without the top left-hand single elastic, I'd have no fears about the Sony falling out. Apparently some of these are supposed to be marked down from ~$50 to $31.47 CAD according to the store's on-line catalogue/stock search, if anyone wanted a cover that came with a notepad, which I admit I'm kind of weirdly tempted by.
I also discovered that even the Kobo Touch cases with the elastics are just slightly too short to fit. Guess I should have stocked up on those $5 clearance Kobo WiFi cases which were apparently just the right size, according to posters on the Red Flag Deals forum, when they were still available, instead of waiting for my Sony to actually arrive before picking up dirt-cheap accessories for it.
But if you wanted one of those fancy-patterned Verso covers which are 30% off in the stores, those are pretty much the right size. I'm hoping they drop a bit more or go on sale for $10 at Future Shop again.