I've featured silent, practice piano keyboards a few times on Squeezytunes. And these have usually generated a fair amount of interest. I didn't know of any current maker of these dummy instruments until Sue left a comment on an old thread here.
There's a piano maker in Cornwall, England called Pinkham Pianos that will make you a five octave dummy keyboard. No prices are given, but their uprights and grand pianos look competitive.
Next we have a virtual instrument from GMedia which emulates string synths. This should be perfect for all your Pink Floyd, Ultravox and Jean Michel Jarre recreations. It emulates 17 different string synths, the full list being:
Nord's Hammond organ simulation was great in their Electro keyboards, but now they've improved it, added an extra manual and also simulations of a Farfisa Compact Deluxe and a Vox Continental. Full details including audio samples are on the Clavia site.
If the Rhodes electric piano isn't flexible enough for you then maybe you'd be interested in the forthcoming Waldorf Zarenbourg which emulates 5 electric pianos, although the website doesn't say exactly which ones.