I used to be a service engineer for cross's and I've done this a few times, rs components and cpc do chassis versions of tft and lcd flat panel monitors, theres usually something you can use and will fit, you just might have to make a shutter out of some black plastic.
Watch out for the video standard, fanuc and heidenhain use some odd ball stuff, some 800 b's have a sync on green video adaptor and some heidenhain's use a strange video standard, you can buy all kinds of video standard adaptors but make sure you know what your getting and that theres a good chance of it working first.
Theres a lot to be said for nipping down the local computer outlet and using a standard monitor, when it screws up you use bin it and stick a new one in, available anywhere, doesnt mach support a touchscreen?, would be cool.