Have you looked at what is available for other cars? Depending on what fabrication tools you have, it may be cheaper/easier to buy one made for another car and adapt it to fit your Mini. I'm not sure about dimensions but the Subaru Crosstrek was the first thing that came to mind: https://ironman4x4america.com/rally-innovations-front-rally-light-bar-mount-kit-with-led-lights-suited-for-2021-subaru-crosstrek/
I’d find someone with a mandrel who can TIG up aluminum, if this were something I’d find appealing. I can’t imagine having an extra 10+ kg of steel hanging out ahead of the front axle and way outside the car’s centre of mass.
I think @Rexsio may be the only one interested in attached a bull bar but I did want to point out that depending on how this is attached, you may accidentally turn a minor fender bender into expensive damage. This may prevent bumps and scrapes to the plastic bumper but the bumper structure is designed to absorb low speed crashes with no major damage. Attaching something in front of the bumper to the car's subframe or other structure could cause some very expensive damage in even a minor crash.
Perhaps the best compromise to get the tough, bull-bar appearance without affecting crash protection would be a squishy plastic foam bull bar (then avoiding automatic car washes).
Ah, but the OP is looking for a way to mitigate damage caused by notoriously bold NYC street parkers!
