Kenai National Wildlife Refuge version
It appears that black widows travel to Alaska quite frequently.
In addition to the Alaska black widow records mentioned in the article, Joey Slowik wrote me that several people brought him black widows obtained from the Fairbanks area while he lived there, which I think would have been in the 2000s.
Today, Bruce King, retired fisheries biologist for the Alaska Department of Fish and Game, wrote to me that he has an adult black widow specimen found in grapes from the Soldotna Fred Meyer last November.
Related media reports
Juneau Empire, August 12, 2002: Black widow spider hitches a ride to Juneau
Peninsula Clarion, May 3, 2005: Lawn chair spins scary tale
Fairbanks Daily News-Miner, April 19, 2013: Alaska girl finds wandering spider in banana bunch