Can anyone mirror this solid for me?

This is not directly a simulation topic, although the model is intended for simulation. Assuming I have friends in this forum, you might be more willing to help out, than in the modeling forum where I'm not known...

Can anyone import this step file, create a "mirror" feature, about the section plane, and create a "mirrored" copy of this imported geometry, and export the result as a solid / step...

I.e. I need the mirrored copy merged with the existing geometry into one solid (original+mirror).

I'm stuck with Solidworks, which it seems, can't do it. ( *frustrated* )

Grateful for any help...