Looks like I can purchase a brand new EA8500 from Staples in Canada. Reading the install instructions:
"If your router is running firmware 18.104.22.168968 and newer, it will refuse the openwrt-*-factory.bin file during the update. Fortunately for non-US versions, it is possible to downgrade to 22.214.171.124978 using the official linksys .img and the “Router Firmware Update → Manual Update” process. Flash 126.96.36.199978 a second time, reboot, verify 188.8.131.52978 has been installed, then you can update using the openwrt--factory.bin file"
Although Canada is clearly not the US, often US versions of items are sold in Canada. Can anyone confirm that EA8500 sold in Canada can be downgraded via the Linksys interface?