3.3V Internal on mini Pro too low for LCD I2C

I wish to increase inside voltage to 5V. How can I do that? 3.3 V is not enough bright for LCD. I know that it can run on 5V. Should I use analogReference(EXTERNAL)?

I am using 9V battery source.

A 9V smoke alarm battery is rated for about 350 to 500 mAh so it won' t last very long but you csn add an LM7805 regulator powered by the 9 V battery to get 5V. Google LM7805.