Brands like Nike are only sold through authorised Nike stores, they operate their distribution through a completely closed network. So you aren't able to source through open wholesale avenues.
Liquidation and factory outlets are about the only open market option for Nike unfortunately.
Nike does, however, take distributor applications. So that may be an avenue worth following up if you were serious about reselling their products, although I would imagine they would set a very high bar you would need to pass to be in with a chance of being accepted.