If you get the appropriate harness setup, carrying the ~50lb corny shouldn't be a problem. As to keeping it cold, a keglove would probably be the best bet. And I'll second the small CO2 charger. It'll be much easier than a hand pump. Sounds like a fun costume, given enough time to construct it.
My jukebox costume weighed at least 40lbs last year. It was a lot of fun, but it was hella hot inside there.
Primary: Strawberry Kiwi Wine
Wifes Secondary: Strawberry Wine
Kegged: Belgian Wit, Belgian Chocolate Stout
Drinking: Irish Stout, Ed's Apfelwein, Chocolate Stout, Holiday Spiced Ale, Irish Red Ale, Watermelon Wine