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The circuitry on that schematics seems to be basically a bunch of PNP transistors in an emitter follower configuration.
The "hard to get" parts are likely those chips with multiple transistors. I assume, that you might try to replace them with discrete transistors of similar characteristics.
Also, by a Google search of the part number ecg2322, I found several helpful hints.
You might do some more research on the matter by "Googling", and even boldly try substitute the quad transistors by some general purpose small signal transistor, which you can buy where you live. The circuit seems to be most likely very non-critical and should work with any normal general purpose parts.
Regarding the problem with high resolutions: You are probably right - the bandwidth is not maybe sufficient for very high resolutions. However, the task is the same: Buffering the outputs. It might require some good high-speed OP-Amps intended for video applications. Hmmm... I have no direct proposal in my mind just now. Sorry about that. You might look at application notes from companies making op-amps.