Patrick Mahomes Fiancée's 'Team Brittany' Shirts Flying Off Shelves, 2K Sold In 1 Day

Hundreds of people are lining up to support Patrick Mahomes' fiancee ... 'cause TMZ Sports has learned thousands of "Team Brittany" shirts have already sold in just one day.

A rep for Charlie Hustle -- the shirt company that partnered with Brittany Matthews to make the tees in the wake of her Arrowhead Stadium champagne celebration backlash -- tells us the shirts have sold so quickly ... there's now a waiting list for the item.

In total, through the first 24 hours-or-so of sales, the rep said more than 2,000 units have been bought.

"The community reaction for the initiative has been overwhelmingly positive," the rep said. "The message that we are trying to convey is to be kind to one another."

As we previously reported, Matthews and Charlie Hustle combined to create the shirts with the goal of stopping bullying.

Matthews said Thursday that the shirt co. came up with the idea after she said she was "attacked" by fans who were putting her down for spraying bubbly following K.C.'s epic win last weekend.

The shirt co. tells us 25% of the proceeds (each tee costs $36) will go to the Red Card KC -- a foundation in Kansas City that aims to prevent bullying -- and Matthews also said she'd be matching the final donation.

Matthews actually stopped by the shirt store in K.C. on Friday ... and was "blown away" by the reaction it's all getting.

"This is just so incredible," Matthews said. "From the bottom of my heart, I can not thank you guys enough."