I have a mercury filled pendulum and need to bring it past customs, what do I do?

We have frequently dealt with this issue, as clients have often bought clocks from outside the United States, and the shipper needed to dispose of the mercury prior to shipping. We manufacture a tube of stainless steel, which we polish to a high luster, that tube is then filled with lead to the approximate weight of the original, and we then manufacture a top of thin stainless that is polished with a bit of a rise in the middle to mimic how mercury sits in a tube, and finally insert the finished piece in the glass tube. It essentially looks identical to mercury, but there is no danger of toxicity.