There are a couple of surprises here - first of all the original power supplies are considered risky to use and may damage the machine. I bought a new one from Electroware;

Electroware New C64 Commodore 64 replacement power supply PSU 5VDC 9VAC

Secondly the C64 monitor port only outputs composite. Still looks good  on my Sony PVM with a SCART cable;

Commodore 64 & 128 (C64 / C128) TV Scart AV Cable