Hello,
I designed this self supporting spool holder for one of my printers, FlyingBear G5, which it had a weak one.
The hole in the middle permits to fix it with a M5 screw everywhere you wish. NOTE: the one in the picture is an old version of the file, which had a shorter opening.
I printed it in PLA, 15% of infill and it doesn't need any support. It fits perfectly on the MK3s' build plate.
Dimensions available in the pdf file.
Enjoy!
The author hasn't provided the model origin yet.