help with v-core 1.3 parts

[midicdj1000]

HI, I am looking to make my own core xy printer from many parts I have on hand and I was looking to use the gantry parts you have shared. XY Joiner Right V1.0 and left. It has a fitting to secure this part to the bearing rails and you are using a captive nut of some type, but I am not able to find what type you have used. So far I have not had any luck with m5 bolt or m5 t slot nuts.

I hope you can help or provide with the older v-core assembly ? I can only find upgrade guides.