99% of all Mickey/Disney items sold outside of Walt Disney World or in outlet stores will have Florida some where across it. 99% of all Disney items sold at Disney World will have it written or logo on the shirt some place.
I would personally visit the Outlet store just off of 535 by DTD, that's outdated merchandise that is no longer sold in the parks. Sometimes you'll find previous year merchandise, but Disney is good at slightly changing a design on some of it's clothing, and you'll find the older items there. It's all marked 50% off of the original retail price, and sometimes if there's really outdated merchandise they'll discount it even lower. We've snagged some really good deals from here.
But avoid the "disney outlet" store in the lake beuna vista shoppes, located on 535 just next to the 417 overpass, there's a VF factory outlet located near the road (which has some really good deals on regular clothes). That disney outlet place seems to get really really old merchandise from disney, and mostly in odd sizes, like a lot of xl or xxl. You might find one item cute or something, but don't waste your time going there. There are some good stores in that shopping center, but not good for tourist shopping. I like going to the VF store and there's a Borders outlet with lots of really good books on sale, and sometimes they have boxes full of 1$ books.
The publix on 535/192 even carries some tourist merchandise. But the Super Target on 192/535, just around the corner from publix, and the Super Target on the far west end of 192 by black lake road, sell "disney" merchandise.
Of course wal-mart at 192/27, 535/osceola pkwy, east 192 (next to medival times), they all sell "disney" merchandise.
And scattered here there and yonder are the crappy tourist trap gift shops.