This is Spool holder designed for 18mm spools (spool's mounting hole). It is 15mm in diameter so can easily manage smaller spools. Designed for Ender 3 mounting, so you can just replace original one with this, the same way like you did during ender 3 assembling. Designed for 200g spools, but i think it can handle 1kg as well, especially with 100% infill, i used 50% and it came really strong. Main mounting is M30x1.5 (Fusion360) thread. At the end it has little end stop so the spool is nocked down. at the end of it is another thread of the same size as main mounting one, so it can be mounted both ways, or added second nut for extra security. Spools should be no longer (hight when putted on flat side) then 90mm. Have fun!
random one PLA
I've printed it without support and it came great.