CTTC has extended their 5G NR module for V2X; you can read about it
here:
https://5g-lena.cttc.es/blog/
CTTC distributes the NR code separately from their repositories, unlike
the LTE models, which were added to the mainline many years ago.
As for LTE C-V2X, the mainline ns-3 does not have such models, but
others have developed them. For instance:
https://github.com/FabianEckermann/ns-3_c-v2x
I suggest to search for 'ns-3 C-V2X' on GitHub, GitLab, and
scholar.google.com to learn about other such models.
- Tom