Maybe you’ve noticed the red trucker hat that Kyle Shanahan, the head coach of the San Francisco 49ers, has been wearing on the sidelines. Twitter certainly has.

“Kyle Shanahan’s hat might as well say ‘I Vape,’” one user tweeted in November.

Another wrote that the retro snapback, with its mesh back, flat brim and tiny 49ers logo, makes Mr. Shanahan look like he’s ready “to host an MTV Real World/Road Rules challenge.” It is “so San Francisco tech bro it’s almost cliché,” in the words of yet another.

Laugh all you want but the so-called Shanahat is sold out in advance of this Sunday’s Super Bowl between the San Francisco 49ers and the Kansas City Chiefs, with no new stock until the end of February, according to New Era, the cap’s manufacturer.