you beat me to it by like 5 minutes :)

Someone from Creality got back to me today. I'm going through the process of getting a replacement through warranty (will keep as spare), but they also told me which dimensions etc i need if i want to order one.

And you're right - Tr8x8, 2mm pitch, 4 starts, 500mm.

just ordered this ReiliaBot one five minutes before i saw your post. Comes with a brass nut.

https://www.amazon.com/gp/product/B07B65RQM5/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

thank you for your help.