Ok tcmtech, that's probably the best bet. I wrote it off in my head as all the mains (240VAC) rated caps I have seen are huge. As this is just 120VAC, it's not so bad... Also, with the use of an extra diode, the converter capacitor can be a polarised type (& therefore smaller yet again).
So rosspt, what do you think of the attached cct? The capacitor should be an electrolytic, 200VDC, >=3uF, minimum ripple current 75mA. Diodes can be e.g. 1n4004 or 1n4007, resistor can be 1/4W or higher.