M5 T-slot nuts for 2020 aluminium extrusion (full plastic)

I'm building a reprap Wilson II printer, and I realized I don't have any t-slot M5 nut which are required, and I can't find any at the local stores... I decided to make them in plastic, even though I didn't have high expectations for them, they proved to be surprisingly strong and good enough for my needs.

There is no threading in the hole, a little pressure and a screwdriver will do the work.

I did a traction test with a portable luggage scale, and I reached 30Kg traction on both the PLA