somehow secure it there (either some redneck engineering or actually custom CNC/3d Print parts)
I'm going to let you in on a little industry secret here: display panels generally come as a bare rectangle, with no obvious mounting locations. The mounting locations you generally see/use are thin brackets that are double-sided taped on, including the Framework displays.
All the OP would need to do is find a screen that is of the correct size, uses eDP, and has the connector in the appropriate spot, and the mounting brackets can be transferred (carefully) from the old display.
The motherboard side is different, but the display side should be standard.