Oh, sorry, I misread.
But wait...
People actually still use 575 machines as a 575? ;-)
I'm not joking that much though because most I've seen tend to fall to pieces, yet the Color Classics I've seen remain intact. I think that's why so many put the 575 guts inside a CC. At least the CC doesn't fall apart.
But as far as replacement back panels for the 575 body, no, I've not a 3D model, probably for the reasons I mentioned. I think we need a polycarbonate replacement case for the entire machine. That way you can be assured it won't crack apart over time.
It's kind of too bad, really. I do see what some folks out there like the 575 as is, or the Macintosh TV, which is rather rare. Just wish Apple would have given more thought into making the case better, considering all that weight inside.