BWE,
To the best of my knowledge you have to be a licensed importer to bring it in, and it has to be marked by the importer. Anyone can export it as long as you comply with ITAR and get the State Department's permission. You would have to deal with an importer on the Bulgarian end for export. I am not an expert on such matters, but in previous research, this is how I understand it. I do believe there are some particular regulations to temporary import, but I am not familiar with them as we were looking at permanent importation. The process seems extremely convoluted, so I would be interested in an "expert" opinion on this one as well.