From what I have read here, the screen is not covered by the warranty, and costs nearly as much as a new reader would cost. But you can contact Pocketbook at
service@pocketbook.com or 877-326-0196. The phone number is US support, but it should work from Canada, too.
I feel your pain; I would be very sad to lose my Might Mouse like that even though I have other readers to fall back on.