Would like a lock for my tailgate on my 1999 Chevy Silverado 4x4 .?

I live in Honduras and would like a lock that I can place on my tailgate that is completely enclosed and can only be opened with a key. I have had my tailgate released and my tail lights stolen and I would like something that would make it more difficult to open. I am a volunteer that works and travels with mission teams that arrive from the USA. I am currently a volunteer with fobf.org, Friends of Barnabas and medico.org from Georgetown, Texas. It is not easey to obtain quality parts and if you do it will cost you and arm and a leg, thanks.