After seeing these online and a few for other model printers, I decided to make one. It comes in 3 parts, a top and bottom and middle. 

I have seen another on here that uses a dovetail slot like the commercial ones, but I couldn't get the fit right on the clearances, so I did this one with triangle shaped notches which should prevent too much backlash, and be a bit more forgiving if you don't have the tightest tolerances on your printer.

The bottom piece is the one with an inset to make it sit flush on your lead screw nut. 

You'll need 4 6mm 3m screws and I recommend 4 washers as well.

If you don't have 6mm screws, you can use 8mm fine on the bottom piece, but the top will need some extra washers to act as shims to keep the screws from interfering with the middle part of the coupler. 

Make sure the pieces are tight to the nut and gantry.

I printed mine in gray sunlu pla+ and greased it with Super Lube.