If your food limitation list is so long as to include all animal products of any sort (vegan) as well as other things like fruit then you are outside what any general catering operation can provide and will, I'm afraid, have to bring your own. Don't forget that liquid restrictions will apply to you, but sauces or similar can be brought through in the permitted-liquids bag in small quantities, and that agriculture restrictions may apply if you are transferring (for example, in USA or in Australia).