I see the trial version for ArcGIS is 10.4 now. Is there any way for me to get a trial of 10.3 ?? I was given an add in product that does not appear to work in 10.4.
Have you tried looking into the student editions?
ArcGIS for Desktop Student Trial
I am not sure that this will be the correct software or not but it may be worth looking into.
If you are a student, you should be able to get the version required from your institute, since they would have the previous versions archived I am sure