What is the most ethical way to pet a cow?

I'm not sure if the question gets across my point that well, so I'll explain it here.

My wife is a vegetarian, and as of several months ago I am working on becoming one myself. Whenever she sees videos of cows online, she always shows them to me, because... well... cows are damn adorable, and she always tells me how badly she wants to pet one.

I would love to, as a small gift, provide her the opportunity to go to a local farm and pet a cow, and spend some time in the fields with the other animals, however, I would like to do this in the most ethical way possible. For additional context, she is anti-zoo, and rightfully so (outside of rehabilitation and reserves of course).

It would be truly awful of me to bring my wife to pet a cow on a farm that principally exists to slaughter their animals and sell their meat to butchers. I'd love to bring her to a place where she can pet a cow that's as close to as "free" as possible. Additionally, something like a petting zoo where at the end of the day the animals are kept in small enclosures and primarily ferried about from stressful foreign environment to stressful foreign environment is a no-go.

We live in Germany, but have regular visits to the US, so recommendations as to a way to be able to achieve this goal that would work in either country would be helpful.

Thanks in advance for helping with this odd request!