Here are websites that allow you to search for dissertations and theses from other counties and regions of the world.
Ethos (Great Britain) Over 400,000 dissertations & theses - some full-text.
Australasian Digital Theses in Trove Limit to format = "thesis" in the advanced search.
Theses Canada Citations and some full-text theses from 70 Canadian Universities.
NDLTD the Networked Digital Library of Theses and Dissertations .
Center for Research Libraries Find citations to dissertations and theses from Center for Research Library member universities. Mostly just citations, but some links to full-text.
DART-Europe E-Thesis Portal Access to hundreds of thousands of open access research theses from 580 Universities in 28 European countries
OpenDOAR - A list of open access repositories online. Search to find out if a university of interest may have a repository, possibly with dissertations and theses online.
If you find a citation for a dissertation or a thesis that you can't find at PSU or online, you can try to interlibrary loan it.
Just click on the link and fill out a request http://library.pdx.edu/services/interlibrary-loan-article-delivery/