Email Matthew Ross
the_matthew@yahoo.ca
Matt will sort you out.. although its probably cheaper just to buy a custom made cable from him then to send your current cable for modification. No adaptor exists.
What I would do if I were you is to ask him to make a universal cable for you. What he does is make one length of cable fitting your monitor, but using a db9 plug on the other end he can actually make adaptors for any console you wish. This will save you buying any more cables in the future.
So you might as well kill 10 birds with one stone and just order adaptors for every console you want RGB from.
Be specific about your audio requirements as well. If the monitor is stereo/mono, if the sound goes via the lead you require or seperate RCA's.. If you want he can put female RCA's on the cable so that you can run cables to any sound equipment you have, or alternatively to your monitor if it takes the RCA's.
this is just an estimate of his prices..
RGB cable for your monitor - $15
Adaptor for each console - $7 - $10 each.
Shipping about $5.00.
I recommend his work, and have about 8 of his cables ranging from SCART leads to XRGB cables.