Flattery would be the best form of approach.

Going in person would be best, start off by describing the good reasons why you want to eat there.

Explain that religious reasons don't allow you to eat any steak.

You know they have high standards but would like to have the chef prepare something you could eat. You'd be happy to bring something along - tell them about the kind of meat you can get and where it comes from, ask them if there is anything you would need to comply with their own standards, basically, just ask their advice about how it can be done.

You'd be paying twice for your steak. Phrase your question right and it's much more a compliment than any insult.