As a normal consumer you can't.
But the predecessor P670 should be available in the SG2380 board in 2024Q3 [0].
It will have 16 P670 and 8 X280 cores, and will cost $120 to $200 (without included RAM).
These cores have just been announced, and are available for licensing. You can contact SiFive if you're interested.
If what you want is hardware somebody's already made, that's going to take 2-3 years as per tradition.
>These are the newest OoO cores with full 1.0 vector extensions, right?
Yes, but so are multiple generations of predecessors. It seems that hardware based on P670[0] and X280[1] (both match that description) will be available for purchase in less than 10 months from now[2].
[0] https://forum.sophgo.com/t/about-the-sg2380-oasis-category/3...