The simplest thing is a Commodore adaptor. It is a chromed 23-pin to 15-pin thing that plugs into the video connector and allows the VGA cable to plug into it. Inside it has a single buffer chip that buffers the sync signals (IIRC), while the video signals are passed through.
Mine has the Commodore part No 390682-01. I don't know if they're still available, though.
A video card is the best bet, if you want to spend money on your machine.
tony
