Thanks for the responses. It looks like I'm going to have to check out the Spencer's in the area. Unfortunately I know all the comic stores in the area and none of them deal in clothing, so that's a bust unless I want to go online as suggested.
edit: Found a pair at the first Spencer's I went to today. Thank again to everyone, Spencer's wasn't even on my list of potential stores since I haven't seen them carry anything MLP previously.
edit edit: Put them on this morning, certainly a tight fit, but I managed to pull them as high as they could go, so they do fit.