Or maybe a simpler profile cut from 20mm plate if the 40mm depth is putting you off... Like this:

Click image for larger version. 

Name:	02_RM1605_ballnut-bracket-20mm.jpg 
Views:	440 
Size:	14.8 KB 
ID:	9344 Click image for larger version. 

Name:	01_RM1605_ballnut-bracket-20mm.jpg 
Views:	396 
Size:	14.6 KB 
ID:	9345

RM1605_ballnut-bracket-20mm.stl
RM1605_ballnut-bracket-20mm.dxf

(I'll make up a proper drawing if there are any takers...)

Cheers!