I received an e-mail from Professor McGrath reminding me of a valuable source on the internet that I haven't written about yet. That is archive.org better known as the Internet Archive. If you haven't visited this site before please do so now as it is full of useful stuff. My search for Mandaeans in the text area brought up three results but if you are familiar with German or French search for authors Lidzbarski and Pognon.
The best part about this site is it lets you view entire books such as Lady Drowers The Mandaeans of Iraq and Iran and you get to choose amongst several formats to read it in. I haven't spent enough time playing around with the site yet to know the full extent of material it has but I'll continue to use it and post about my findings.
Another resource that I have found has great possibilities, accessmylibrary.com which by providing an e-mail and a public library card number you can gain access to all the data they have. This being said I should clarify that the data that they provide is more along the lines of listing what is available in the libraries that this site is associated with making it one giant card catalog. I am holding out hope that they may grow to include PDF's of their magazine articles in the future but there is no way know whether that will happen or not.