Robin, I would call or make an in-person visit to the firms that are refusing to use you, first of all.
Then I would find out what equipment or qualifications are required to for international depos and meet those qualifications.
My first depo was no different from being here in the US, except for the electrical hookup. Different countries require a different adapter. You need a passport. And if you get requested to do one of these jobs, I would HIGHLY recommend that you pick up a book on etiquette for that country and the status of the person you're taking...hope this helps.