I found the original at Thingiverse (https://www.thingiverse.com/thing:3036241) but the "hook" to attach the strains to was a bit to flimsy and weak for me (actually broke two times on two models while attaching the strains).
So I removed the hook, widened the hole at the front and introduced a small "tunnel" for a zip tie or similiar.
It fits my needs perfectly and maybe somebody else can make use of it, too.

Credits to "Kattstryparen" for the original design.

HEvo 3D (Core XY)

No

No

0.2

25%

To improve stability, I used three wall lines and six bottom and top layers. Rock-solid even with only 25% infill.