LT1308A - High Voltage Modification
[EDITED to replace circuits and restate the current part.]

First, please note that the output is raised using a voltage tripler.



So the first thing can be to replace it with a voltage doubler.



Then you have to change the ratio of 10M and 34.8k resistors so that for 180V output you get 1.2V at FB pin. For example instead of 34k8 you put 68k.

The current seems to be limited by 50% efficiency of circuit. The converter alone peaks 90% efficiency at 200mA switch current. If this is the case, and efficiency is not improved, you can aim at 2.5mA max output.

Source of circuits