Need to test my app on Nexus 7

Recently I published my app, which is build on top of OpenGL Es 2.0 … and this is exactly what causes problems: On some devices my app does not render anything, the screen remains black.
Especially the Nvidia GeForce ULP GPU seems to be a problem (during compiling the shaders, a message about gradient calculations, which may not work, appears, but I was not told, what the log looked like exactly), but I do not have access to a device with this GPU! The app runs perfectly on my own device, on all my emulators, and on almost all devices of the Samsung Remote Lab … and there is not a single device with a Nvidia GeForce ULP GPU on the Samsung Remote Lab.

Any advice what I could do? I do not have the budget for buying this device, or spending > 100 $ a month on commercial services like Perfecto Mobile. In my case automated test services are useless completely and utterly, as it’s nothing I could write unit test cases for, I need an actual Nexus 7 device for testing my app interactively until it works.