I just uploaded some STL's in a 'no insert.zip' file on thingiverse that remove the need for the heat set inserts.  This should help if you are having issues finding inserts or the ones you find don't fit well.  Keep in mind that this is a weaker setup, however it is how my original version worked and that held up for the most part.

I originally got my inserts from Initeq, if that helps anyone having issues finding them locally in the US.

3mm heat set inserts

5mm heat set inserts