Like Grant, I have never seen it for sale in the form you describe. You
might have better luck going 'higher' in your assembly tree if the
assembly resembles something available commercially. For example (maybe
not relevant in your case), you can buy leadscrew-drive machine
tables/slides in an incredible variety of sizes and precision.

If you can share a little more specifics of what you have in mind, you
will probably be deluged with suggestions here!
--
Fred R
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