finally I found a solution. This is how I made it: I took a like in the source file of your SVG dots and saw that you used Sketch. So I downloaded a Trial version, and loaded our pink dots in it. Then I clicked on the image in he Sketch window and it offered to copy the code of the SVG file. Next i pasted that code into my netbeans editor and saved it from there as SVG file. I bet there`s an easier way to export the SVG from Sketch but I could not find it.
but in the end I could create an SVG file with smaller dimensions and the following CSS made it look nice on the borders:
border-image-slice: 33% 22%;
border-width: 0 0 8px 0;
border-image-outset: 11px 5px 10px 4px;
Thank you again for your help!