Is it possible to get a master's in speech language pathology online or part-time?
There's at least one program at the University of Wisconsin in Eau Claire. It's designed as a part-time, online master's. You're required to attend 3 one-week sessions on-campus each summer over three years. 

If you don't have an undergraduate degree in communication sciences and disorders, there are 30-40 credit hours of required courses - PDF before you can start the master's.