You're best bet is to google away for a vendor. Just be sure your LCDs can be mounted as some lend themselves to be so, others especially non-similar brands may pose a problem. Your quest is not uncommon, but I don't deal with such vendors on a regular basis. I suggest you check: http://www.blackbox.com and http:www.jdr.com others for a source.
Looking for dual LCD stand or arm to hold 19'' Dell E193FP and 17'' Samsung 710N. Any recommendations?