Interestingly, I have had this happen on numerous occasions, particularly with international magazines. You have every right to send a bill to the producer's of the magazine. AND you have the right to charge them a full price, rather than your 'typical' discounted price.
I've also had similar things happen with newspapers. In those instances, it's important to balance what relationship you may need with that paper in the future, as whilst they may eventually cough up payment, you'd be hard pressed to ever get them to write a nice article about you.
I wish you every success
Fr Bill