Need gantry rails & screw rod to convert growth 4x4 to 4x8

I bought the growth series roughly 10 years ago to find out a few years ago that they no longer support the growth series. When I bought the 4x4 there was no 4x8 available and I was told it was coming soon. Oh well. That didn’t work out.

Anyway, I really need 4x8 capabilities. Where can I buy the custom ground rails that the gantry bearings roll on, and the screw rod that is turned by the motors to move the gantry?

I assume I can by the plastic cable guides somewhere online.

Thank you.
Drew.