5V to 160V DC converter
Not really a whole off-the-shelf part, but... A small step-up converter with an autotransformer sounds just right (flyback converter without isolation).

Also, you could try something like figure D1 on page 93 of Linear Tech's app'note 47 (without Q1 and the three resistors and the capacitor around it, just to the point that says "avalanche bias"). Adjust the divider to the FB pin for 160 V instead of 90 V. This little circuit is a combination of a step-up converter and a charge pump.