If anyone else needs the part, here it is.
It involved a bit more work than just mirroring the section. I also had to change the top cutouts as on the original part, they were offset slightly from the centre of the part
There is also another way to get the part but the quality is far less.
You get the pitching in field cad from this post:
2021-2022 VEX IQ Challenge: Pitching In
…and then you take out that part.
However, the quality looks really poor (atleast for me on onshape), so that may not be a good option for you