iPad as external monitor: vertical/portrait mode unsupported

I love using ipad as a second screen for traveling. One thing I regret is not being able to use it in the vertical mode. I don't particularly care about the aspect ratio other than more compact footprint. But, unfortunately, the screen is polarized with the expectation of being used vertically, and using polarized sunglasses makes it very dark even at full brightness when horizontal, making non-polarized sunglasses necessary for using outside :)

Are there any workarounds enabling vertical mode?