How to adjust pilotless water heater for high altitude?

We just got back from a week of camping at 9500 feet -- great trip! But the water heater struggled -- if I did not leave the cover completely open, it would soon quit. With the door open, it worked ok. This is one of those newfangled pilotless things.

Is there any way to adjust the burner so that it will stay lit at high altitudes? We are hoping to go to Colorado one of these days, and there are campgrounds at 10,000 feet or higher.

Thanks in advance for your advice!