From a quick google, I think the four axis board uses the same controller - eg;
Do you mean the one in this article for the 3040T 4-axis version?
https://hackaday.io/project/6776-304...og/20946-day-1
It uses a JP-382A and an extra JP-1635A for the fourth axis. If so, you just need to install another stepper controller, which could be that model if your box fits it, or any 24v stepper controller, which could be as cheap as $10....
But if you're going to do it that way and you can't just fit the board in as pictured, and you need to rehouse everything, then you can still replace with a USB 4-axis controller and 4 stepper drivers for less than $100 and just wire them up as a new setup using the same PSU in a new box.
Hope this helps - I'm a bit new to the forum and inexperienced, but no one else mentioned anything so I thought I would.
David.