This is a modified version of Synthetic Electron 3D's Internal Spool Mount design. I added 5mm to the spacer to give the spool more room and keep it farther from the print bed. With this change, you can also remove the spool without needing to lower the bed all the way.

You can download the spool and small cover piece files from their original page, and don’t forget to give their post a like while you’re there.

Print the Top/Bottom Files twice.