It depends which output your C64 has there were two version a 5 pin DIN & an 8 pin DIN. The 5 pin version only give out a Composite signal, while the 8 pin version gives out both Composite & SVideo.
You can easily buy 5 & 8 pin din connectors here in the UK and I'm pretty sure you'd be able to find them online in the USA.
I've never had a power supply problem with any of my C64s, even the one I still use today is from 1985 and still runs perfectly. So personally I don't see the need for any sort of power protection.
Your right about that other site on closer inspection it does look a bit sketchy..