I tried fussing with the Dell/HTC audio strap model on here, but I didn't want to remove the rear adjustment strap just to slip it on.
I ended up just sticking the stock cable clip in my scanner and scanning and extruding it LOL.
Worked a treat! Use it for your own attachments!
Scan with a normal flat-bed 2D scanner at 600 DPI in black and white. Copy and paste into 3D builder, and size in one dimension, then extrude to proper dimension.