Uninterruptible Power Supply... 110V AC and low current (60 milliamp)
if if bulb requires AC to operate it's not simple (easiest to buy an off-the shelf UPS), if it will run of 170V DC it's simple but potentially exciting.

So have a bridge-rectifier feeding a big fat capacitor via a resistor.
you could maybe scavenge the bits from an old PC powersupply.

the result will be a lamp socket with DC on it (and both terminals live) so assuming Edison screw base for the lamp potentially exciting.