Tim,
Glad to help.
Trackside Publications has published a number of books whose subject are generally South American railways. It has a website at:
http://www.tracksidepublication.com/
This small specialty press was operated by Donald Binns for years and published his writings and those of others. One of the other authors, Christopher Walker, took over Trackside Publications in June of 2008 (information from the website). The website seems to have been added since the change of ownership as I had never found a website before.
The website says that its titles are available from Salida Roundhouse in Salida, Colorado. phone and email contact is listed.
In the past I have used the English booksellers shipping overseas. I will check them every few months to find books that are never advertised in the American publications.
Brian Norden