I guess you could try hdmi>dvi>vga adapter's. That's an absolute longshot for that to work, but to this point I don't believe there's a good solution to do this. When I had my PS3 for a whopping 2 weeks, I searched and searched.. I just got rid of mine because the version I had didn't play PS2 games.
If all else fails, you'll need to get a monitor that supports digital inputs.
I was searching a bit, and from what I have found, your monitor needs to support HDCP, and when converting HDMI to VGA, you won't get a signal, unless you get an converter, which costs a lot.