I've never seen a VGA 50hz capable lcd monitor in my life. Well, the ones I looked at given a certain price range. Perhaps Eizo have them or Sony professional (broadcast) monitors, but they are VERY expensive. If you really need realtime switching (for what purpose?) then you'd be better off with a dual monitor setup. If you have a pc, you can use the dvi input as well, and span the monitor in Windows XP for extra large real estate :-D
But, again, I don't know your budget and if you have room for a solution like that.
edit:
Buffy is out indeed (looks at empty bed) :-(
Actually I tried to change my avatar but no luck, animated gif's aren't accepted :-?