TMZ Sports is told ... the NFC champions received new bling from The GLD Shop's private popup outside their Levi's Stadium locker room last weekend ... right before flying out to Sin City for their matchup against the Chiefs.

We're told "Mr. Irrelevant" and Co. got pendants of either the classic SF logo or 49ers helmet ... each plated in 14k white gold.

The dope ice also came with rope chains or upgraded diamond tennis necklaces -- like the one Purdy has on his neck in the pic above.

We're told the players loved their gifts so much ... some of 'em purchased more at the popup shop -- from diamond watches to iced-out chains ranging from $1K to $50K!!

The GLD Shop founder Christian Johnston -- who has worked with A-list celebs including Rihanna and Kevin Durant -- also gave fans a chance to get the same 49ers items (as well as other teams) this Super Bowl weekend at the Mandalay Bay Convention Center in LV.

"We're excited to be back at the Super Bowl," Johnston said.

"Being part of this major sporting event in the entertainment capital is a genuine honor. We're ready to rise to the occasion, bringing the ice to Las Vegas with NFL Crown Jewels -- an immersive experience that lets fans across the nation rep their favorite NFL team with style."