120vac to 180vdc @ 300ma, non-isolated current-limited
The simplest way is to use an inexpensive power transformer with a 120 volt primary and a low voltage (about 12v) secondary. 

Connect the two windings in series as follows to boost the transformer output voltage up to the sum of the primary and secondary voltages (in this case 132 volts).


Connect one leg of the secondary to one leg of the primary.*
Apply 120 volts across the primary. Between one leg of the primary and the other leg of the LV secondary, you'll have 132 volts!


132*1.414=186 volts P-P. Feed your 132 volts to a full-wave bridge rectifier, and filter the DC from it with a capacitor, and you'll have 186 VDC no-load. 

A 12 volt secondary may or may not be high enough to get 180 VDC @ 300 mA. However, Mouser has them in various secondary voltages, with and without a center tap. (While you're at it, buy a suitable fuse and holder!)

*The secondary has to be connected in the correct phase, so that the voltages add.