If you do not mind the adapters you could use a Key Digital Systems( KDS ) Flash 4 which switchers 4 RGBHV inputs to one RGBHV output. I suspect they could sell the adapters as well. And Crestron has the C2N-MMS which is exactly what you are looking for but I would guess more product then you require.
Extron makes a very good System 8 or System 10 switcher which is high bandwidth and handles 8 or 10 channels of RGBHV all through BNC connectors. A bit out of peoples price range new ($3000) range but they can be had on Ebay for anywhere from $200 up. I got lucky and found one at the local electronic flea market for $50. It even switches the channel and projector settings for the different inputs on my Marquee projector. Search on ebay for Extron switcher and sort through the offerings.
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