I have tried most all of the filament clips and none would sufficiently hold my filament. I received a similar clip with a spool of filament that worked well, so I tried to duplicate it's main attributes, which would securely hold 1.75 mm filament to the edge of the spool.
*** UPDATE ***
Added "SmallFilamentClip.stl" file that is the same clip but with a smaller opening so it will clip securely to spools with thinner sidewalls.
You can also heat up the corner of the clip with a lighter and bend it so that it clamps more securely to the filament spool.
