There are 3 levels of Disney merchandise available:
1. Official Authentic Disney Parks merchandise
2. Authorised Disney merchandise
3. Knock-off (unauthorized) merchandise
The only place I know of to reliably get the Authentic Parks stuff is the two Disney Character Outlets at the Premium Outlet Malls. These stores are operated by Disney. Vineland is closest to BC. This is usually older or seconds merchandise that has rotated out of the parks and is reasonably discounted. There are other outlets not run by Disney that seem to mix the first two types of merchandise.
There is lots of Authorised merch as well. Our favorite stops are Target, Publix, and
WalMart (in that order). All 3 have locations handy to BC, either South (192) or East (535/Turkey Lake). This is where we grab souvenirs for friends and family.
Then there are the shops along the major routes like Irlo Bronson (192) that offer "5 T-Shirts for $10" sort of deals. Cheap (price), cheap (quality), and most likely not Disney (or Universal) authorized. Not recommended.