As Arthur said, check eBay for Dial Intercoms, or maybe some of the folks on the site might have one available. The units are usually identified by a Letter and a number. T-10 is a tone only, 10 station unit. R-19 is a rotary only 19 station unit and a C-36 would be a combination (rotary or tone) 36 station model.
There are slight variations - some units offered "dial tone", most did not. Some could be converted to multi-channel, most could not, etc.
Earlier dial intercoms were large, cumbersome things. When the new models, essentially the size of a trade paperback, came out, the others all went away.
The new ones connected with a single amphenol cable. You punched them down on a block and connected power in and signalling out.
Sam
