Decided to make a round filament spool holder for the Fabrikator Mini. It's a little heavy on the materials, as the cylinder is fairly wide to allow for easy rotation of the spool. (This one is also designed for a full size 1kg spool, rather than the .5kg spools Hobby King suggests for this machine, and which many of the other spool holders I've found are designed for.) Many of the "square" holders on Thingiverse will use far less plastic as well. Nothing wrong with those designs- I just saw an opportunity to make something a little different & practice design in Tinkercad.

Printed the first copy of this on my Monoprice Maker Select i3, and it came out fairly well. And in a testament to the wonders of digital calipers, it fit like a glove! There is less than 5mm of clearance between the full size 1kg spool and the extruder, so it is a close fit, but it should work fairly well. My only lingering concern is how well it will work with a full spool, and whether or not the weight of a full spool will cause any tipping issues, or if the extruder motor will have trouble with the extra unsprung weight.

Once I get a brand new spool to try out, I'll update this description. For now, I at least know it fits like a dream. Which shocked me, since it was my first draft.

***Update 12 August, 2016: extruder does not appear to struggle with the full sized spool, machine does not tip with full sized spool, but if I push it backwards, the tipping point is not terribly far back. So I printed some support feet found here on Thingiverse, by user drofnas: http://www.thingiverse.com/thing:1396469

I also imported that design into Tinkercad & cut it down to make matching front feet. They are all a great fit, and the rear feet make the machine feel very stable with a large spool hanging off the back.

This thing was made with Tinkercad. Edit it online https://www.tinkercad.com/things/aOR9d1Xys07