Print an STL and its mirror?


Hi! I would like to print an STL and also print its mirror. I don’t have a tool to do that and understand that this can be done in most printers.
Is this possible?
I would put an order of x2 of the STL, but where would I write the request regarding the mirror to make sure that is what I get?

I printed with Danels Hub and was pleased with the work, and wanted to use his service again (as I thought I could just message him) but messaging is now disabled after the service has been provided. This means I won’t be sure I’ll get what I need.

Any tips?