1.5V to 5V dc-dc converter
If the designing of a boost regulator is not the primary objective, use a pre-built boost module such as this one ($1 including international shipping from eBay):



The module works with inputs from 0.9 to 5 Volts, and outputs 5 Volts at up to 600 mA.

Of course, you would have to wait 3 to 6 weeks for the delivery, but at the price, that might be worth it.