Here we have the .STL file to 3D print your own 3D printer filament cleaner.
Print out the model and insert a piece of sponge into the filament cleaner. Poke a hole through the sponge so that the filament can pass all the way through the device. Soak the sponge with a few drops of mineral oil and then insert the filament through the filament cleaner somewhere between the filament spool and the extruder. If you have a filament guide tube make sure that the cleaner is positioned before the filament enters this.
We would, as always be grateful to hear how you get on with this. There are some evolutions of this design on Thingiverse as well, specifically designed for the Makerbot Replicator.