Sounds like a homebrew project to me! If the voltages will be "applied to plates inside an instrument in our lab," will there be any significant current drawn in the steady state? How about during switching (changing) voltages? How fast must the potential applied to a given plate settle to its final value after changing from a previous value?
My approach to this (if the current demand is small) would be to use a single 60 VDC power supply driving 10-15 MOSFETs as source-followers, one each in series with the plates. Use voltage feedback from each plate to control the gate-source drive to individual MOSFETs. Use multiple digital-to-analog (DAC) converters to set the reference voltage for each feedback circuit. Pay attention to the open-loop phase/gain characteristics to avoid oscillations when the feedback loop is closed. You may have to resistively load the outputs to obtain a stable circuit. And you will need some sort of computer interface to control the DAC outputs, perhaps integrated with whatever effect the instrument plates produce.
This doesn't sound like a beginners project, but there are people here that can help you.
@KrisBlueNZ has considerable experience designing MOSFET circuits and perhaps can suggest a DAC-adjustable 0 to 60 VDC circuit along the lines I described. A lot depends on your project budget and design goals. If this is a one-off experiment that will be later abandoned, but you have a budget that allows for disposable electronics, then there are plenty of high-voltage op-amps available that can provide the outputs you need with minimal fuss interfacing to a DAC.
I am not aware of any off-the-shelf digitally programmable power supplies available at reasonable costs, but Google and other search engines may locate something suitable. I would look for surplus programmable NIM (nuclear instrumentation module) power supplies of the type used to bias avalanche photon detectors (not photomultiplier tubes!). However, as you noted, most commercial items will be over-specified for your needs.
Please describe in a bit more detail exactly what you are trying to accomplish, time window available to do so, and your budget (if any).
